Why Fast? Part Two – Cancer

fasting cancer“Everyone has a physician inside him or her; we just have to help it in its work. The natural healing force within each one of us is the greatest force in getting well. Our food should be our medicine. Our medicine should be our food. But to eat when you are sick is to feed your sickness.” – Hippocrates


“Instead of using medicine, rather fast a day.” – Plutarch

or even:

“No kibble today, thanks. I’m feeling a bit under the weather.” – Fido

For thousands upon thousands of years (during most of which overweight, let alone obese, people were fairly rare), therapeutic fasting was a common protocol for the healing of many a malady. From famous sages like Plato, Aristotle, and the aforementioned Hippocrates and Plutarch to cancer patients unable to eat during chemotherapy to pet dogs and cats who suddenly lose once-voracious appetites upon falling ill, it seems like the natural response to – and perhaps therapy for – major illness is to stop eating for a while.

Now, “natural” is not always good. “Is” does not necessarily imply “ought.” But I think the persistence of this phenomenon throughout nature demands that we look a little more closely into whether or not there’s something to it. From babies putting items they found on the ground into their mouths to introduce novel bacteria to their bodies, to weight lifters craving meat after a hard workout to introduce protein to their hungry muscles, to pregnant women experiencing strong food aversions to minimize the chance of introducing a toxin or poison to the growing fetus, I’m generally of the opinion that there’s usually a physiological explanation for most of our odd cravings and behaviors. I see no reason why a sudden lack of appetite wouldn’t have a similar explanation – especially one that transcends species. What if skipping meals for a day or two kickstarted internal healing in some way? Is that really so outlandish? You already know where I stand on the importance of lessons learned from watching our animal companions, and I think this time is no different.

Luckily for us, we aren’t just flailing around and making guesses. Modern science has deigned research into the phenomenon, particularly regarding cancer, worth pursuing. According to Valter Longo, a cancer researcher from USC, “normal cells” go into survival mode during starvation. They display “extreme resistance to stresses” until the “lean period” ends, much like an animal in hibernation mode. Cancer cells, on the other hand, are always “on.” Their “goal” is to grow and reproduce and consume resources. For cancer cells, there is no novel survival mode to switch on. If this is the case, fasting should both improve our resistance to cancer and our body’s ability to survive it (and the treatments used against it, like chemotherapy).

Though human trials are scant (you can’t exactly inject people with cancer cells and then try out different therapeutic protocols, the animal research is intriguing. Let’s take a look into the literature, shall we?

Animal Trial

In one of the earliest studies, forty-eight rats were split up into two groups of twenty-four. One group ate ad libitum for a week, while the other group underwent alternate day fasting. After one week of the various dietary protocols, both groups were injected with breast cancer. At nine days post-injection, 16 of 24 fasted rats remained alive, while just five of 24 ad-libitum fed rats lived. At ten days post-injection, only three of the 24 ad libitum-fed rats survived; 12 of the 24 fasted rats remained alive. Pretty large disparity, right?

That was in 1988. It wasn’t until the late 90s that more promising research was undertaken. That’s when Longo began studying in earnest the phenomenon of increased cellular resistance to oxidative stress during fasting. Figuring that since chemotherapy exerts its effects on cancer by inducing oxidative stress (to all cells, not just cancerous ones), and fasting triggers survival mode in normal cells but not cancer cells, he conducted a study on mice to determine whether fasting protected the healthy, normal cells from chemotherapy’s side effects while leaving the cancer cells sensitive to the treatment. Tumor-ridden mice were either fasted or fed normally 48 hours prior to a large dose of chemotherapy. Half of the normally-fed mice died from chemotherapy toxicity, while all of the fasted mice survived (PDF). Furthermore, fasting did not improve the survival rate of cancerous cells, meaning it only protected normal, healthy cells.

Research has continued. Longo found that “starvation-dependent stress” protects normal cells, but not cancer cells, against the effects of chemotherapy. Even a “modified” alternate day fasting regimen, in which mice were given 15% of their normal calories on “fasting” days, reduced proliferation rates of tumor cells. This “85%” fasting regimen was even more effective than the full 100%. And most recently, Longo et al found that fasting both retarded the growth of tumors while sensitizing cancer cells to the effects of chemotherapy – across a wide range of tumor types. Most importantly, they concluded that fasting could “potentially replace or augment” certain existing chemotherapy regimens! That’s not some crazy fad diet guru spouting off about ancient traditional wisdom, folks. That’s a cancer researcher.

Human Trial(s)

There has been just one of which I’m aware: a 2009 case study that delivered promising results. Ten cancer patients – four with breast cancer, two with prostate cancer, one each with ovarian, lung, uterine, and esophageal cancers – underwent fasting prior to and after chemotherapy treatment. Fasting times ranged from 48-140 hours prior to and 5-56 hours after; all were affective at reducing side effects of chemotherapy.

In the first case, a 51-year old woman with breast cancer did her first round of chemotherapy in a fasted state of 140 hours. Other than dry mouth, fatigue, and hiccups, she felt well enough to go to work and resume her normal daily activities. For the subsequent two rounds, she did not fast and instead ate her normal diet, and the side effects were extremely pronounced – severe fatigue, diarrhea, weakness, abdominal pain, nausea – and prevented her from returning to work. For her fourth round of chemotherapy, she fasted, and the side effects were again minimized. And it wasn’t just the subjective effects that improved with fasting, but also her physiological markers. Total white blood cell, absolute neutrophil counts, and platelet counts were all highest after the fasting regimens.

More human trials are underway, however. Hopefully we’ll eventually know whether the loss of appetite commonly reported during chemotherapy treatment is a bug or actually a built-in feature (I’m leaning toward the latter, personally).

Other Possible Protective Mechanisms of Prevention

Improved insulin sensitivity. As I showed in last week’s post on fasting and weight loss, intermittent fasting improves insulin sensitivity and reduces insulin resistance. Insulin resistance has been linked to several cancers, including prostate, breast, and pancreatic. Metabolic syndrome, which fasting seems to help prevent and reduce, is linked to cancer in general.

Autophagy. While autophagy – the process by which cells “clean up” cellular “garbage” – has a complex relationship with cancer, it’s generally a positive process that protects cells from excessive oxidative stress. Fasting has been shown to induce “profound” neuronal autophagy, as well as general autophagy.

Fasting versus caloric restriction.

It’s true that caloric restriction appears to offer anti-cancer benefits, but there are a couple ways in which fasting might be superior:

1. Fasting (acute bouts of caloric restriction) is easier than CR (chronic caloric restriction) for most people. As I mentioned in last week’s post, fasting – for some – is just an easier, more natural, more effortless way to reduce your calorie intake. That can pay huge dividends when it comes to weight loss, and it appears likely that it will help with cancer, too. If fasting is easier than constantly counting your calories, fasting is going to work better.

2. Fasting is more effective in a shorter amount of time. Whereas studies on caloric restriction and cancer employ weeks- and months-long CR regimens, studies on fasting and cancer employ hours- and days-long fasting regimens. In most cases, fasting just seems to require far less time to be effective.

It’s an exciting time for fasting and cancer research. While it’s still viewed in most circles as an “alternative” modality, fasting is now being seriously considered as a possible treatment (both adjunct and even primary) for various cancers, including breast and prostate. I can’t wait to see what comes out in the coming years.

Of course, my own feeling is that fasting is both easier and more effective if you have made the transition to a Primal Blueprint way of eating. In other words, when you have up-regulated those fat-burning systems and down-regulated the reliance on glucose, many of the other issues that can make fasting less appealing to “sugar-burners” tend to go away: cortisol levels out, muscle protein is spared, hunger subsides naturally and energy is steady.

What does this mean for you – the person who either has cancer and wants to get rid of it or who doesn’t have cancer and wants to stay that way? Researchers like Valter Longo can’t officially recommend it to cancer patients, but it seems well-tolerated and basically safe. If you or anyone you know has cancer, suggest fasting as a possible strategy. As long as a person keeps their oncologist apprised of the situation and any relevant research on the subject, it might prove helpful. And if you’re currently cancer-free, consider implementing occasional (intermittent) fasts, just to be safe. I know research like the stuff I’ve just outlined has convinced me that it’s definitely worth a shot, and there’s little if any downside.

For those of you readers who currently practice fasting, do the potential cancer benefits motivate and drive you? If you aren’t currently fasting, does this evidence make you want to? Thanks for reading!

Here’s the entire series for easy reference:

Why Fast? Part One – Weight Loss

Why Fast? Part Two – Cancer

Why Fast? Part Three – Longevity

Why Fast? Part Four – Brain Health

Why Fast? Part Five – Exercise

Why Fast? Part Six – Choosing a Method

Why Fast? Part Seven – Q&A

Dear Mark: Women and Intermittent Fasting

TAGS:  prevention

About the Author

Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.

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174 thoughts on “Why Fast? Part Two – Cancer”

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    1. I mostly have lots of soup when I have a cold (“Jewish penicillin” although not just chicken.) I haven’t had the flu since starting primal two years ago but probably would fast if I did.

    2. Right on, Mark. Fasting right now. Appreciate the “Fido” quote – the first thing a pup does when it’s sick is to stop eating. Another example of animal instincts trumping human “intelligence.”

      1. Don’t mock human intelligence for it was this very intelligence that found out about this correlation.

    3. i have the rarest of the neuroendocrine cancers, one of which killed steve jobs; 12 years ago i was told by the some of the leading experts that if i did not do chemo immediately i had 1 month to 1 year to live. my inner animal/muse/soul told me that poisoning my body was insane, so i did watchful waiting until my tumors were forcing rapid descents in blood sugar i do not have an insulinoma; i am a somatostatinoma, but my tumors behave as the former oma does; when my bs was at 35 despite eating every 12 hour i had a whipple and liver resection; one of the aforementioned experts sent a letter to my magnificent & brilliant neurosurgeon telling him ‘you will kill miss mason’ hah!

      i now control the fatal hypoglycemic plunges by doing a 24 hr water fast

      however, years ago i used to do 3 day fasts & always felt reborn

      i am now expanding my weekly fasts to 3 days and am in touch w dr. longo

      i will have offered my cat scans, labs, slides, etc to dr longo but any legitimate researcher who wants them is welcome to them

      jeanette mason

      1. Is there any chance that your ‘3 day water fasts’ caused or contributed to the illness you developed?

    4. I fast and it does wonders for my acne and well being. I fast with honey and pollen as my only energy sources. I drink lots of wáter.

  1. Very interesting read, Mark. I have also noticed that periodic fasting seems to have some psychological benefits. Specifically, I feel more focused during fasted days. Are there any supplements that you would recommend taking during a 24hr fast?

    1. I always drink (organic, grass-fed) gelatin powder in water as it has enough protein to protect muscles and is great for healing the gut, especially when you aren’t eating. I also take probiotics because they are more effective on an empty stomach, and magnesium before sleeping.

    2. That really depends on your goals during the fast. Green tea contains the compound EGCG, and drinking it during the fast is a great way to end the lives of stubborn fat cells. In addition to autophagy, which will promote unused and mature fat cells to die, drinking green tea during the fast, will cause fat cell apoptosis. Coupled with the fat-buring effects of fasting and the autophagy induced, you will virtually become a slaughterhouse for unwanted fat cells. You could also supplement with the extract of green tea.

      I promise I’m not a tea fanatic, but I also prefer to drink Yerba Mate during the fast. I already find the mentally stimulating and calming effects a fasting a huge motivator for fasting. I attribute this to neuronal autophagy, and increased catecholemine levels. But, drinking yerba mate adds another dimension to the stimulating effects of the fast. Don’t use sweetners of course. Also, try drinking coffee and see which one you prefer. Both increase catecholemine levels. Coffee is more intense though.

      1. I have been doing IF for several years now. Unfortunately when I drink Green Tea or Yerba Mate during a fast I will end up throwing it back up within 30 minutes. I never have any issues with coffee.

        1. Wow– I drink a gallon of Green tea and have no nausea at all. Coffe is fine too and ice water.

          I usully begin my fast after a large cup of coffee with a little half and half–at 5am, then my next meal when I am IFing is the next morning– 4 eggs and coffee.

          I do this once or twice a week and I love it.

      2. I have the same issue, I get nausea right away. Coffee is fine though.

      3. hi, Mathew,

        thanks for the information on green tea & yerba mate

        i have heard some anecdotes of weight loss using green tea from a friend & her friend.

        i usually fast 16 hours everyday by skipping breakfast. occasionally longer (18 – 24 hr). my brain rather enjoys the clarify.


    3. I find that I’m more focused as well. I was surprised to notice this change, which is welcome because there are plenty of times when I can’t seem to focus at all.

    4. +1 on the psychological benefits including increased focus, although I noticed the opposite before switching to a primal diet.

    5. I just got Yogi Tea, “Healthy Fasting” blend to use with an upcoming fast. It was recommended to me. It says it has Red Clover, Burdock, and Dandelion for liver detox. Usually I just do water whenever I feel thirst.

      The other thing is the duration of the fast. Lengthy fasts should be supervised since electrolytes and minerals could be exhausted. Something short (I do 3 day fasts) could incorporate some juicing (for the nutrients).

      Another thing I’ve read (over at LeanGains) that if the goal of the fast is to burn fat, coffee (organic and not decaf, again diluted) to keep the metabolism from going into starvation mode.

      So I guess the original question, which supplements, depends on the goal of your fast.

  2. The benefits just continue don’t they? I have an 86 year old uncle who had prostate cancer. He fasted before and after his chemotherapy, not because he knew anything about it but just because he didn’t feel like having anything other than water. He took the bus back and forth to the hospital before and after his sessions and said they didn’t really bother him that much. It amazed me when I heard that, but possibly the fasting part was why.

  3. Ok, ok. I don’t like the idea of fasting but I will start doing it. (Blood sugar still a bit to high and a family history of cancer.)

  4. This does make me want to fast, but every time I try, I end up super-cranky and super-hungry. It seems like frequent small meals works well for me, as anti-Primal as that sounds. Maybe I need to eat more overall so the fasts mean something. I’m not sure — if anyone has a thought on that, I’m all ears!

    1. It took a while before I could fast without these issues. Headaches, shakes, crankiness…I know what you speak of. After about 8 months of eating primal, though, I started being able to skip meals without issue.

      Recently I’ve started skipping breakfast. I drink some coffee with cream, and that’s “breakfast”. Though I get a bit of a gnawing hunger, it’s nothing I can’t subdue with a few sips of coffee. I’m ready to eat by lunchtime, and by then I’ve usually held off eating for approximately 16 hours.

      Like Mark mentions, this is way easier for me than caloric restriction. But I would not have been able to do it if I hadn’t been primal for a while. Attempts to try this in my high-fiber, low-fat days always met with failure.

      1. it also took us months to be able to fast for > 12 hours.

        i also have black tea + 1 TB heavy cream for breakfast.


    2. Try eating a fairly protein-heavy meal a few hours before bed. I prefer to eat eggs because the protein digests slowly. In the morning most people have a naturally blunted appetite, so this is going to be the best time to fast. You will be fasting through the night so when you wake up you will have been fasting ten hours. Try to go a few hours and then break the fast when you feel like you need to. Try to push it out a little more each day, or every other day if you prefer. Try to stick to the same fasting periods if you plan to do it frequently as the hunger-regulating hormone, grehlin, will tends to spike around our habitual meal-times.

      1. That’s what seems to work best for me. At night or pretty late in the afternoon, I try to load up on 1 lb. of grass fed beef or pork or fish, 8-12 pastured eggs, etc. When IF’ing, if I eat the last meal in the afternoon, I typically will eat again sometime around noon (10-2) the next day. But, if I eat pretty late, I may go until mid or late afternoon the following day. A 16 hour window is about average. However, sometimes I may eat late and then I may eat early the next day (a shortened window). Or I may eat early and then wait until late the next day (a lengthened window). Or I may graze throughout the day (eat without worrying about any windows). I kinda like mixing it up the best rather than sticking to a set routine.

    3. I used to get like this, but I found that after I started doing few workouts on ’empty'(i.e. training first thing in the morning and also after work when my blood sugar is normally at its lowest, but not every day of course) I stopped getting cranky and having dizzy spells when I was fasting.

    4. An “accidental” 24 hour fast last week left me gnawingly hungry, shaky, confused, cranky, and nearly incoherent. But I’ve only been paleo for a month now, so maybe I can work up to it over time.

      IF of the “early dinner, skip breakfast, late lunch” variety works great for me already – I don’t notice any hunger at all and feel great doing it. It’s also clearly helping me a lot with weight loss.

      1. If you get shaky, have a bit of bragg apple cider vinegar with some raw honey and water.

    5. Sounds like you’re still carb addicted & possibly not eating enough good fats, that response is typical of a sugar and glucose metabolism & low blood sugar.

      If you’re properly in ketosis & fat burning mode your body, in response to a lack of food from fasting, will just start burning your stored body fat and will just continue making ketone bodies for energy which, if you are in ketosis, it has already been doing. There is a break in period, known in the Atkins & Medifast circles as the Induction Phase, I call it CARB WITHDRAWAL, where it can take several days to a week or more to completely condition & get your body accustomed and ‘acclimated’ to running on fats instead of glucose from carbs.

      Try increasing the amount of fat in your daily diet all the time, not just before attempting a fast, decrease your carb intake, don’t eat ANY carbs for dinner the night or even the entire day before starting a fast, then in the morning your body will already be in fat burning mode and then just don’t eat.

      Keep trying, don’t give up, you’ll get it, your body naturally WANTS to burn fats, that’s what it does while you’re fasting, it’s the carbs that are UNnatural in the human diet.

    6. Little meals here and there do work, and I agree it can be hard to fast. Your brain is fighting you every step of the way and demands food making you cranky.

    7. Also, try eating once a day. Only hi quality food; half of it raw, etc.

  5. Since going primal I lost 50lbs and stalled, since incorperating 2 24-36 hour fast twice a week and a 48-60 hour fast once a month in 2 months I lost another 20lb and haven’t ever felt better than I do now. Also doing heavy lifting while fasting is great and actually improves my numbers. Fasting for weight loss is a great tool, everything else is just a bonus 🙂

    1. Sweet! I too dropped 45 in four months, from 286 to 240, but have been dragging along this plateau for a few months now. I think I let all the complements people have been givivng me go to my head and falling back on the 80-20excuse. I am still 30 lbs away from my goal. I just started p90x and will start a fast tomorrow. Thanks for sharing and reigniting my motivation!

  6. After reading some material on Martin Berkhan’s Leangains site, I’ve implemented his version of IF: restricting eating to an 8-hour window. This lead me to discover that I need more protein at each meal to forestall hunger. Finally, I’m in the process of cutting down to just two, high-calorie meals/day, further reducing the time I expose my body to insulin (which I seem to overproduce in response to food).

    It’s impossible to say whether this will prevent cancer, especially since I don’t have a family history of it. My main objective is to have a more comfortable time maintaining my weight loss (40 lbs). But if I develop cancer, I will try the “15% solution.”

  7. I practice intermittent fasting right now as part of my weight loss regime. It’s worked very well for me, I try to do at least two 24/hr fasts a week and I’ve found them very easy to stick to.

    Cancer benefits seem like icing on the cake to me.

  8. I agree. I’ve been Paleo for 2 months as of March 18th, and begin IFing shortly there after. I try and do 1-2 24 hour fast a week, but that doesn’t always happen. I eat only when I’m hungry and so sometimes I end up fasting for 12-18 hours, unplanned. I love not having to think about constantly eating to keep my metabolism “revved” up. It was the best day of my life when I threw that idea out the window! Life is so much more enjoyable now. In the last month, I’ve noticed a significant decrease in my body fat percentage, my clothes are fitting better and I’m PRing in most things! All this while not even counting a single calorie. It’s awesome!

    1. I feel exactly the same. I struggled so much trying to eat so often during the day – just remembering to prep food all the time, trying to have 3-4 small meals on hand during my work day, trying to find time between meetings to eat it all – ugh! I felt like I was miserably choking down food constantly and it did me no good whatsoever.

      I’m so much happier now not having to worry about it – if I don’t have time to make food for lunch at work, so what? I skip it and feel find till dinner. Just this single change probably cuts my cortisol production by a quarter every day. 🙂

  9. Although I’ve not researched it intensively, I’ve studied some level of similiarity regarding cellular resistance toward oxidative stress when fasting as you discuss, or supplementing with resveratrol. I can see how the research you cite can show benefits of fasting. If there’s a lot out there about resveratrol as well, I could see how both could be extremely useful in many ways.
    Thanks for another great article, Mark

    1. Re resveratrol – it was just recently inthe news that one of the lead researchers into this faked a lot of his data. You may want to look a little more closely before you leap.

  10. This topic of fasting is extremely interesting. I have done some 8 to 10 hour fast in recent months and am planning to do a 5 day fast to facilitate my weight loss. I am in need of some advice on what vitamins are necessary to take during an extended fast. If anyone could chime in on this I would appreciate it. Thanks

    1. You might want to consider limiting your fast to two or three days, then eating a big meal, then resuming your fast. I say this because leptin will drop off sharply, usually around 3 days without eating. Your metabolism will slow down and you might start to experience symptoms of anhedonia. You should have a doctor supervise you if plan to be fasting past three days.

  11. I’ve been trying out some IF lately and am wondering if my GreensPlus in the morning will negate the effects? There is no sugar or macronutrient content, although it is sweetened with stevia.

    Also, would coffee throw a fast off? What about that tablespoon of coffee cream?

    Just trying to figure out where to draw the line on these things coffee makes fasting so much easier 🙂

    1. If it has negligible calories then it won’t throw off the fast.

      Coffee is great during a fast because it will increase levels of epinephrine and norepiphrene, causing you to feel mentally sharp and calm, as well as increasing your metabolic rate. These hormones are also responsible for burning fat. Can you believe I almost left out that fun fact?

    2. Do not use ANY processed grocery store powered or liquid coffee creamers, use full whipping dream or butter as per Dave Asprey’s bulletproofexec butter coffee recipe.

      For protection from cancer induced by toxic foods you absolutely MUST read the ingredients list on EVERY food you buy, particularly any industrial processed “foods” you may still be using or eating, and THE SINGLE most overlooked product people use on a daily basis is coffee creamers, this stuff is killing huge numbers of Americans & other people around the world.

      Most coffee creamers are adulterated with partially hydrogenated trans fat soy, corn, coconut, palm or other industrially processed vegetable oils which are a direct cause of cellular hypoxia & oxidative stress by blocking oxygen & nutrient flow into & out through the crucially important bi-lipid cell membrane.

      The ONLY liquid coffee creamer I’ve found that does not contain the toxic partially hydrogenated trans fat oils is Nestle’s Coffee Mate that’s packaged in the little restaurant style cups with the tear off foil lid. This one is made with non adulterated coconut oil and so does not require refrigeration since coconut oil is such a stable saturated fat molecule, even pure raw organic coconut oil can be left at room temp for up to 2 years before going bad, it’s very stable which just one of about 12 reasons coconut oil is so good for the body.

      To be fair, now that I check their website I see Nestle is offering a new product with ingredients listed as NONFAT MILK, HEAVY CREAM, SUGAR, NATURAL FLAVOR CONTAINS MILK.

      Meh, since pretty much all commercially processed milk is toxic I’ll just stick with Dave Asprey’s bulleproof butter coffee.

      1. Unfortunately, if you check out the shop ethical website, Nestle has a boycott call on all of their products. they employ irrisponsible marketing methods, promote bottled water (you have to have 6000 glasses of tap water to reach the same cost of 1 bottle of bottled water, also, the plastic is not recycled efficiently)Nestle also is responsible for using child labourers, denying workers rights, ties to violence, poor wages for coffee farmers and their also irresponsible users of palm oil. They have been targeted by greenpeace for supporting palm oil production and deforestation in Oraungutan habitats. I believe that now we are primal and healthy for ourselves, we have a responsibility to pass on that health through our chices to support a more sustainable Earth and future. Otherwise, we are being pretty selfish in our new found health and wellness. Support the Earth which supports us.

  12. I just wrote today on my blog about meeting someone with cancer at Paleo FX and what sorts of thoughts about this lifestyle it prompted in me. I certainly hope for his sake, and all of our sakes, that some of this stuff we’re ardently advocating works.

    1. Cancerous cells convert to fermentation for their energy from the normal “respiration” or using O2 to burn glucose of a healthy cell. A fermenting cell requires up to 20X the glucose as a normal respirating cell. Therefore, low carb eating and IFing is the natural enemy of cancer cells as you are literally starving them and/or preventing their formation in the first place. Another factor is the body’s PH which high carb diet turns acidic which is the environment cancer “grows” in.

  13. When I had severe pneumonia earlier this year, the first thing to go was my appetite. There I sat in front of Christmas dinner, and I couldn’t eat it.

    Did my very first fast last Friday. Planning another one this Friday.

  14. That last quote should have been credited to Buddha…but that would have confused some

  15. I’ve just started trying to get back into a fasting routine and this post really lit a fire under my rear! In my family, I’ve got my dad who had lymphoma, grandparents with a brain tumor and breast cancer and aunts who have had breast and uterine cancer. I originally started fasting to break my current plateau but now I have a whole new motivation. Cancer is the #1 disease I feel like I have to fend off and it’s nice to have a weapon to do it with.

  16. Thank you for posting a very timely article for me! My husband is undergoing treatment for multiple myeloma and has experienced loss of appetite as a result. At yesterday’s appointment, he was told he lost too much weight and needs to maintain body fat in preparation for the stem cell transplant in May. (The nurse actually recommended daily hot fudge sundaes–AAAAGH!!)

    My question is… When he was first diagnosed I researched fasting. I remember coming across an article that said it was very effective for certain types of cancer, but not helpful (maybe harmful?) for blood cancers such as multiple myeloma. Did you come across any research to this effect?

    BTW…At the start of treatment we bought a container of Primal Fuel and it has been one of the few foods he can tolerate when he’s feeling his worst. Thank you for the blog and all that you do!!!


    1. Thank you for mentioning about how blood cancers may react differently. My mother also has multiple myeloma and is about to start the stem cell transplant. I wanted to research this a little more to see if it is something that can benefit her. She also has very little appetite, but from what she says it seems it is because the taste of food is different. Good luck to you and your husband.

      (also, can I second your “AAAGH!!” at the food they say she should eat which includes “bread, sodas and pastries” and the do not eat list included so many good vegetables, it just makes. me. sick.)

    2. FYI- my mother(66yrs) was diagnosed last year, did the chemo rounds 4 mos, with no side affects, and had stem cell transplant in November last year- never seen her so sick those first few weeks after, but can’t believe how quickly she bounced back! She is doing great and we are so fortunate to live in the present day, medicinally speaking. I wish your husband all the strength in the world as he goes through his “new birthday” (you’ll see). And I might add that you need to make sure you are taking care of yourself while he’s in the hospital, go home and rest, keep exercising and getting some sunshine. Resist the urge to “suffer with him”. He will be doing enough for both of you those first couple weeks, so you have to live healthy for the both of you during this time to offset.. Positive love and affirmations to you and Stephanie.

  17. I do a bi-weekly (or every 2 weeks) 24 hour fast. I do this to help clean up metabolic waste, normalize blood sugars, promote healing and to exercise control.

    I didn’t have much success with fasting when I used to drink coffee. I really feel drinking coffee deletes the benefits of a fast. Your adrenal glands don’t get an opportunity to rest.

    I have been caffeine free (coffee, tea and chocolate) for a little over a month. It was a life altering decision. I have the same stable energy all day. I do feel hunger more intensely now than when I drank coffee for a fast, or just in general, but I use this to practice control over not spending my days strung together with food and drinks.

    I try to enjoy the day and live it instead of relieving constant boredom and a mind-numbing job with spikes to serotonin levles.

    Fasting has been a great tool for me.

  18. I am overdue for this myself. I have done some on and off since reading the Bragg book, Miracle of Fasting, a while back. I lost about 40 or so pounds and have kept it off for 2+ years. I have to agree that fasting is easier than eating less. I did a longer juice fast once and while it wasn’t to bad, I think the juice may have made it a little more difficult.

  19. I’m starting to get into fasting everyday from 8PM-4PM the next day. It seems to work very feel for me when I get accustomed to it. Unfortunately when I fall off the wagon and eat in the morning, subsequent days are harder to fast successfully.

  20. I have fasted for a day here and there and always find my energy increases when I fast. I have even done some extreme exercising while fasting, and think I even have more energy for then. I am thinking about adding fasting to my routine, but am trying to figure out the right mix for myself. In any regard, my limited experiences have been very positive.

    1. If you want to fast every day, you can experiment with confining your eating window from anywhere between 8 and 4 hours. You could even do one meal a day if you can eat enough in one sitting.

      Also, eating at night and fasting in the morning generally feels better for most people. This is due to naturally elevated cortisol levels in the mornings. If you fast at night, cortisol may be elevated, and you may find it hard to relax and sleep.

      1. That explains a lot. I’ve been fasting from last meal on Sunday until Tuesday morning which is around 36 hours. Monday night I can’t sleep at all, even with magnesium and melatonin. I don’t want to give up the whole 36 hours but is there anyway to sleep?

  21. There are lots stress resistance effects of ketogenic diets as well. Can we try to tease out some mechanisms? I suspect it has something to do with alternative “fuels,” protecting mitochondria and maintaining stable energy production.

  22. This is blowing my mind-grapes. It could help explain so many things, from why severe bouts of stress and depression can kill appetite (so your cells can deal with the stress hormones), to why so many cultures have “purifying” fasts before times of physical or emotional trial (again, so your cells can deal with stress hormones and damage better), to the old wives adage, “Feed a fever, starve a cold.”

  23. I have a stage IV cancer that has a 5-year survival rate of 5%. I have been the living primal lifestyle except for I do not have energy enough to exercise properly(this could be due to the one drug I am taking – an anti-estrogen medication since my cancer is sensitive to estrogen). Oncology doctors never talk diet it seems. When I ask them, all they say is, “balanced diet with some protein – would you like to see the dietitian?” During Chemo I saw the dietitian, spews the same old CW.

    I was aware of the rodent studies on fasting when I went through Chemo (Chemo is an absolutely horrible experience, at least mine was). I asked my Dr. whether he knew anything about fasting before doing chemo. Of course not, but it was okay to fast the day of chemo if I wanted, but not more. So, I didn’t.

    Just a week or so ago, Dr. Su (Carbohydrates Can Kill) had a cancer researcher on his podcast that experiments with low-carb diets to treat cancer – Dr. Seyfried. If I’m remembering correctly, he said it only works if calorie restricted enough to get your blood sugar down to 55mg/dk to 65mg/dk. That was very disheartening to hear. It’s hard for me to keep them under 100. So maybe my efforts to control my blood sugar haven’t been saving me.

    I also read things about autophagy, so I figured it would help to fast. I’ve been doing 18 hour fasts everyday.

    My main cancer Dr. prefers to treat based on symptoms, rather then taking multitudes of CT scans like my chemo drs. like to do. This is to my liking as I have been avoiding scans in hopes it would help me heal by avoiding the dyes and the radiation they involve. The cancer I have has no good tumor markers for blood testing either. I can’t say that my cancer has not returned as I just don’t know at this point. But I’m coming up on 2 years and I’m still here. I’ve yet to find anyone else doing paleo or primal who has cancer – am I the only one?

    1. Johannah as someone who has finished chemo for stage IV hodgkins lymphoma 4 months ago, I think I know how you feel. I wanted to improve my diet while on chemo to combat the lethargy (although it was pretty healthy according to CW). I like you was spewed out the saw CW by the dietatian. Having stumbled across marksdailyapple I experimented and found it helped me alot. I have now been primal for 4 1/2 months and have recovered from the side effects chemo pretty quick suprising my doctors and myself.

    2. Johannah as someone who has finished chemo for stage IV hodgkins lymphoma 4 months ago, I think I know how you feel. I wanted to improve my diet while on chemo to combat the lethargy (although it was pretty healthy according to CW). I like you was spewed out the saw CW by the dietatian. Having stumbled across marksdailyapple I experimented and found it helped me alot. I have now been primal for 4 1/2 months and have recovered from the side effects chemo pretty quick suprising my doctors and myself.

      Hope you all the best.

      1. Suhail,
        Thank you. I recovered from chemo well too. They tell me now that except for having cancer, according to my bloodwork I’m pretty healthy which does seem to surprise them. Wishing you great success for the future.

    3. Johannah check out the website chrisbeatcancer.com ! Chris follows the paleo diet and he also has a lot of information about holistic treatments for cancer. Send him an email and he is happy to give advice about what worked for him and other success stories.

    4. I have been working on healing my whole body and changing my internal terrain to ward off a breast cancer diagnosis. (I’m 31 years old.) I have not had any conventional treatments other than a biopsy. Part of this decision is due to the fact I was 11 weeks pregnant when diagnosed… now 35 weeks. I was eating primal before the diagnosis, but right after, I was concerned about my level of meat consumption as most alternative cancer diets say to cut out all meat products. (Not sure I agree on that one.) My body craves meat and I pretty much felt awful. I spent the first few weeks doing a lot of fasting, mostly due to emotional stress. I have been eating only veggies, nuts and meat for the last five months plus Cottage cheese and Flax oil…. part of the Budwig protocol. I had been eating fruit too, but cut that out as well. Cancer cells have way more sugar receptors than normal cells. The tumor is estrogen/progesterone positive and that has been challenging since during pregnancy, those levels skyrocket. Anyway, you are not alone. Greendrinkdiaries.com is a great blog of a young woman who beat her cancer using diet as a main part of her protocol. Best wishes to you! P.S. I feel better physically than I have ever felt in my life. I know nutrition has a lot to do with that… I know prayer has helped too! 🙂

      1. Harobe,
        Thanks and I’ll check out the website. Wishing you a healthy delivery, happy baby and a wonderful future!

    5. The secret to maintaining energy and immune system strength when dealing with cancer is FATS & PROTEIN. If you cut out the carbs that simply feed cancer the sugars it needs for energy to grow, all you’re left with is fats & proteins anyway. The only other option is a total food fast, so combining the two can be very effective.

      If you want to know more about cancer than 95% of the doctors & oncologists who have never even heard of or been taught about Otto Warburg & his Nobel Prize in 1931 for the discovery of the prime cause of cancer go here: https://goo.gl/xE5eL

    6. You’re right about the paleo diet being naturally highly protective from cancer, and that’s so for several reasons:

      1. Cancer is easier to cause than to prevent. All you gotta do is eat a Standard American industrially processed ‘food’ high carb & trans fat loaded diet. The problem is that the latency period for the development of cancers is measured in decades. It’s so gradual that by the time people are diagnosed with cancer they DON’T associate it’s development with what they’ve been eating for the last several decades, so the best time to get off that SAD & processed ‘food’ diet is 20 to 30 years ago.

      2. Cancer is easier to prevent than to ‘cure’ and a fresh & natural whole food paleo or low carb diet, or even a Pritikin, Ornish, Gerson, Atkins, Hoxey, vegan, vegetarian, green smoothie or almost any other nutty diet theory works by first getting you off the toxic industrially processed foods & toxic adulterated vegetable oils that directly cause cancer and replaces those ‘foods’ with real high quality nutrients that deeply feed and nourish every cell and, more importantly, every cell membrane in your body.

      3. The main cancer protective component of a paleo or primal diet is the high quality natural fats, and also the proteins and amino acids & oxygen carrying heme iron in them. Think about it, every cell, cell membrane, major organ, hormone, enzyme & bone in the human body is made from fats and proteins in varying quantities, they are the 2 main raw materials the body needs for cellular repair & rebuilding.

      I would, however, seriously caution anyone fighting a stage IV cancer to avoid *strenuous* exercise so as to not further deplete your energy and immune system. It’s got a big fight on it’s hands and is already working plenty hard, trust me. You need to save as much energy as possible for your immune system so it will be as strong as possible to fight off the cancer.

      Remember that the only reason any of us get sick and develop various diseases and illness in the first place is because our immune systems become depleted and weak and can’t resist and fight off the invaders anymore and at some point are overwhelmed. That energy and immune system depletion is usually caused by what we’re eating rather than from exposure to toxins or something outside of us. The lack of appetite or desire for food during an illness is the body’s natural energy conservation strategy, at those times it doesn’t want to devote energy to digestion of foods and instead wants to direct as much energy as possible to increasing it’s immune system strength so we survive the illness.

      If you like getting out in the fresh air to enjoy nature you can take gentle walks, but since only you can feel what your body is doing and what it needs let it be your guide as to your level of activity and physical output. Also wouldn’t hurt to consult with your care providers since you didn’t mention talking to them about exercising while fighting cancer.

      Good luck, much love, and may all the gods bless you and all yours during this time.

  24. I love the appeal to ancient wisdom in the introduction. There is so much our ancestors knew and spoke about, and we take so much of it for granted.

    My fiancee often feels like skipping meals, and she never feels like eating breakfast. In fact the other night she asked me, “I know it’s dinner-time and I need to eat something, but I just don’t feel like eating. Is that bad?” Being a practicing IF’er myself I told her that it is GOOD for her not to eat when she doesn’t feel like eating.

    I wonder how many other people would have thought the world was ending if a loved one skipped dinner.

    1. There was a time when kids would be sent to bed without dinner for misbehaving or some other offense, but these days parents can get thrown in jail, have their kids taken away by the government and have a REALLY hard time, a permanent record, continued government intrusion & oversight & much expense getting them back for doing that, so if it happens at all anymore I’m sure they’re not talking about it.

      1. I don’t think punishing a kid with (or without) food is the same as fasting, and can cause food issues in a person. But, if a kid just doesn’t want to eat dinner, that’s a totally different thing.
        I have no problem letting my daughter eat when she wants to eat – even if it isn’t at the same time as us. Sure, I make one meal and she can eat it when she’s hungry. I find she’ll eat a wider variety of foods if she is allowed to wait until she is actually hungry to eat. But, punish her by not letting her have dinner – no, absolutely not. I would also never force her to sit there until she finished her food (like my parents would do when I was growing up).

        1. Just last night I sent one son to bed without supper for not doing the dishes. It’s not going to kill them. I don’t force them to clean their plates either, but I would make them sit for an hour until they at least taseted the food.

  25. I am so happy to see this article! I am fasting today and feeling like I am the only one not eating. I fast four times a year at the equinoxes and solstices as well as during religious fasting days such as lent. I do this for health reasons and for building mental, physical and spiritual discipline.

    Plus, how much more paleo can you get? I don’t think Grok was always successful in his hunts and spring time is historically the hungry time of the year.

    1. You reminded me of something I wanted to bring up.

      If Grok was unsuccessful during a hunt he probably foraged for his calories. Of course hunting provides ten to a hundred times as many calories as foraging, so getting calories from foraging was probably menial. I imagine this is why 15% of calories had a more protective benefit

    2. John – what a lovely way to celebrate the seasons. And it’s the spring equinox tomorrow!

      Not sure I can cope with fasting during a crazy work day, but I’ll join you by fasting in the evening.

  26. This evidence strengthens my ability to articulate why it’s beneficial to fast but I was motivated by how good it made me feel even though I don’t need to lose any weight.

  27. Great information here, Mark. I did a 22 hour fast day before yesterday and was happy that it was so easy. My weight loss had stalled at 42 pounds and I still have another 80 to go. I’ve decided to do alternate day fasting for a couple of weeks and see what happens. The anti-cancer effects have strengthened my resolve. Thank you and sending positive thoughts to those suffering from cancers of any type.

  28. I haven’t been doing any 24 hour fasts or anything but I HAVE been skipping more meals lately. Usually breakfast. I just noticed that I haven’t had to go to the grocery store yet this week and I still have plenty of eggs in the fridge. YAY Eating less=a smaller grocery bill this month. Who knew??

  29. “It’s an exciting time for fasting and cancer research. While it’s still viewed in most circles as an “alternative” modality”

    Did you know the word “alternative” is based on an ancient Greek word that means “Big Pharma can’t make billions of dollars in profit on it”?

  30. Intermittent Fasting…

    I’ll get to the IF in a bit, please hang in there with me.

    Here’s my story. Lost 120 pounds on Primal, gym and later crossfit (for last 20lbs of the 120 crossfit gets that honot), I was down to 270 (at the time could still use to lose another 20-30) fitting in my old 36 inch pants (admittedly they were just a tad tighter than I would care for but I could at least put them on and not have them bursting at the seams). But no IF, couldn’t do it. Along comes life, stress and some bad times and BAM! I turn to old comfort food ; you see there is a bakery down the road that makes the best cream doughnuts and they are my addiction (now I avoid them like heroin, as that is how I view them – as a poisonous drug and I don’t really have a choice once I take that first bite). from the end of October until January I put on 50 pounds. Fast forward to March. After much withdrawal and misery, I am once again full Primal and have added IF, almost seamlessly by the way. I am down 20lbs in a little over 30 days. No loss of strength by the way. I have to admit I have come to enjoy the mild challenge. Knowing that food is there but that I choose to abstain. I also like the fact that it has made shedding weight that much easier. If I have learned any humbling lesson it is that the Paleo/Primal way, needs to be considered in its entirety. To leave out one part is to potentially miss out on great benefits. This is of course with the understanding that every part of the Primal blueprint will not necessarily work for everyone. However if not investigated how would we know. I admit I was dummy for dismissing IF the first go around.

  31. “do the potential cancer benefits motivate and drive you?”

    After reading that post, it certainly is an additional motivating factor. I fast for spiritual growth and only recently began fasting for the physical benefits. I am VERY careful to keep the two seperate!!

    This is why I am a little more excited about fasting after reading this post, Mark: I’m 48. My mom and dad both died of cancer. My dad when he was only 40. 18 months ago I had colon surgery for severe displaysia. The doc said there is a good chance I wouldn’t have seen my 50th birthday had it not been cought when it was.

    The current “wisdom” seems to be that we don’t need a colonoscopy until we’re 50. Well, current “wisdom” is just playing the odds and that’s playing the odds with YOUR life. One thing I really want to stress to everyone is GET A COLONOSCOPY ASAP!!! Don’t wait until you’re 50!!

    1. And eat plenty of good staurated animal fats, primarily BUTTER!

      From Wikipedia re butyrate: “Butyrates are important as food for cells lining the mammalian colon (colonocytes). Without butyrates for energy, colon cells undergo autophagy (self digestion) and die.[1] Short-chain fatty acids, which include butyrate, are produced by beneficial colonic bacteria (probiotics) that feed on, or ferment prebiotics, which are plant products that contain adequate amounts of dietary fiber. These short-chain fatty acids benefit the colonocyte by increasing energy production,and cell proliferation and may protect against colon cancer(2).”

      It’s been known for years that people that avoid good fats have the highest rates of colon cancer, now you know why.

      1. Thanks, cc! I’ve been enjoying bacon and bullet-proof coffee ever since I happened upon Mark’s site. Also, I’ve started cooking my steaks with butter.

    2. And from Wikipedia search, Butyric Acid (as found in butter):

      “Cancer And Life Span
      The role of butyrate changes differs between normal and cancerous cells. This is known as the “butyrate paradox”. Butyrate inhibits colonic tumor cells, and promotes healthy colonic epithelial cells;[11] but the signaling mechanism is not well understood.[12] A review suggested the chemopreventive benefits of butyrate depend in part on amount, time of exposure with respect to the tumorigenic process, and the type of fat in the diet.[8]”

  32. Would there be a way to implement the cancer-chemo benefit of fasting for a person who is not overweight and maybe on the line for being underweight?

    1. Yeah, do a carb fast, meaning eat lots of good fats & some good animal proteins but nothing made IN an industrial plant, just plants & animals that eat plants.

    2. Absolutely! Just make sure to eat your maintenance calories (or above) during your eating window. For example, if you maintain bodyweight at 2000 cal/day and you fast for 16 hours every day, just make sure to eat at least 2000 calories during your 8 hour eating window every day. Or, if you want to do alternate day fasts, look at your calorie intake over a week long period. If you only eat every other day (and your maintenance is again say 2000) make sure your calorie intake adds up to 14,000 (or more) over a 7 day period and you should not lose weight.

  33. I started lifting weights 6 months ago and paleo dieting soon after. To my dismay, I didn’t find myself losing the post-two-babies weight I wanted to lose. I told my trainer I think I must be ‘immune’ to weight loss. That’s when he told me about fasting. I love it so much. Having 2 little kids at home, there is no way on earth I would give up coffee or wine, both are essential parts of my day, so I drink a couple of cups of coffee in the morn, fast all day, and then at dinner have whatever I want…and wine, and the pounds keep coming off. It is such a liberating feeling to know that I am in control of my body now.

    1. “Having 2 little kids at home, there is no way on earth I would give up coffee or wine, both are essential parts of my day”

      I LOVE that, Robin!! And congrats on the weight loss.

  34. Robin, how often did you fast? i’ve just started fasting and have done 2 24 hour fasts in the past week or so, i just dont know how often i need to fast in order to get rid of the extra 40lbs im carrying!

  35. As someone who just finished a year-long immunotherapy for Stage IIb Nodular Malignant Melanoma, I can attest that during the first month of treatment, IV Infusion 5x a week for 4 weeks, my side effects were definitely better on the days when I did not eat before or after. I will point out however that it only helped with the digestive part, not the fatigue. I am a firm believer that your body knows what it needs and when!

  36. Animals fast when ill–we’re animals. I water-only fast at least a couple times a year from 5-10 days just to clean out the accumulated micro-junk. I’ve said for years that if I get cancer my first move will be to fast. Fasting allows the body to do repair when not over-burdened by digestion, which for much of the population is nearly constant.

  37. Paleo has allowed me to endure a pre-op 12-hour fast that turned into a 16-hour fast–it took the docs an extra 4 hours to get their shit together to remove a large splinter that had lodged parallel to my finger bone.

    Happy thing was: no pain afterward. I tore up and threw away the prescription they wrote for Oxy when they sent me home. Not bad for MY FIRST SURGERY EVER! I think next time I’ll do the fast WITHOUT the finger surgery–I already eat only twice daily, so it shouldn’t be too hard.

  38. https://www.nutritionandmetabolism.com/content/7/1/33

    Metabolic management of glioblastoma multiforme using standard therapy together with a restricted ketogenic diet: Case Report

    This is the first report of confirmed GBM treated with standard therapy together with a restricted ketogenic diet. As rapid regression of GBM is rare in older patients following incomplete surgical resection and standard therapy alone, the response observed in this case could result in part from the action of the calorie restricted ketogenic diet.


    Targeting energy metabolism in brain cancer with calorically restricted ketogenic diets

    Our results in mice with brain tumors together with previous studies in children with malignant astrocytoma indicate that brain tumors are potentially manageable with dietary therapies that lower glucose availability and elevate ketone bodies. These diets target tumor energy
    metabolism and reduce tumor growth through integrated anti-inflammatory, antiangiogenic, and proapoptotic mechanisms of action. While diet therapies are not part of the
    current medical practice in the brain cancer field, we are hopeful that physicians and patients will come to appreciate their value in managing malignant brain tumors.


  39. Hooray! As a melanoma survivor, and someone who wants to stay cancer-free for the rest of my life, I really appreciated this article! I haven’t really implemented fasting in my regular regimen, but when I do feel “off,” the first thing I do is not eat.

  40. My quick question is: has anyone heard of IPT (insulin potentiation therapy). In short, cancer cells feed on gluclose, and are most vulnerable to chemo after feeding and preparing to divide/split into two cells.
    I have read articles with research that IPT before chemo accomplished two things: 1) chemo was much more effective b/c of cancer cells vulnerability while splitting, 2) dosages of half the amount of chemo or less used with IPT were way more effective then full dosages of chemo without IPT.
    I was obviously wondering about the possibility of combining a pre-fast with IPT before chemo to try and incorporate the advantages from both into chemo treatments effectiveness.
    Don’t know if this could work/be helpful, but wanted to roll it out there and see what people thought.

    1. Yes, have heard of IPT and a carbohydrate restricted or ketogenic high fat & protein diet would be a requisite part of & enhance IPT so as to target and direct the chemotherapy drugs to the cancer cells specifically.

      If there’s anything to the theory at all it’s that IPT works by taking advantage of the fact that cancer cells do in fact have 6 to 10 times more insulin receptors than normal tissues, along with the fact that cancer cells have high glycolytic rates & requirement for sugars due to their use of the glycolysis process for energy production.

      So it wouldn’t make sense to try IPT while maintaining a high carb diet that regularly stimulates lots of insulin production and keeps all of your bodies insulin receptors full of and accustomed to regular deliveries of insulin. The chemo drugs are combined with insulin, NOT glucose or sugars from carbs, so keeping your body in a fat burning ketogenic mode keeps all cells starved of sugars AND all insulin receptors starved of insulin so that upon administration of the insulin /chemo mix hopefully it would go directly to the cancer cells first, or exclusively, because of their higher number of insulin receptors.

      If I was dealing with any serious late stage cancer I would seriously consider IPT a viable option. My studies and research about what cancer is and how it operated has taught me that cancer is orders of magnitude easier to PREVENT than to cure, but in a life or death scenario I personally would not be afraid to pull out all the stops, within reason of course and with my physicians guidance.

      Hope that sheds some light on the issue and helps answer some of your questions.

  41. I use modified alternate day fasting combined with a small eating window every day, primarily for weight loss right now, but have come to realize that I am very comfortable with the situation. I eat about 500 cals on low calorie days and 1500-1800 the rest of the time. On the low days, I don’t have anything but coffee and HWC until about 4:00 pm and generally delay eating till 8:00 in the morning or later the next day–about 12-16 hour fasting period every day. I am looking to increase the fasting hours.

    I feel great! I prefer the lower days, honestly. I expect to continue this type of meal “schedule” for the long term. This, combined with healthy Paleo food and movement, is my “retirement fund.”

  42. interesting post. I recently have started eating less because I just wanted to.

  43. Due to candida, I’ve only been eating about once a day for the last few weeks. I honestly feel great, and figure, if I’m not hungry, and am having issues with digestion, why eat?

    It really does makes sense logically, and it gives your entire body a break. I drink lots of tea (huge yerba mate fan here as well!), and feel great.

    Some days I start to trip out a little, HA! But that’s an added bonus of fasting!

    I’m very happy with the results I’m getting. Less really is more!

    Thank you so much for these latest articles, Mark. They are fascinating!

    1. Like cancers, systemic fungus and fungi in general make energy by using glycolysis, fermentation of sugars. That’s why mushrooms can grow in absolute dark, they don’t use photosynthesis and sunlight to produce energy because most fungus does it’s work of breaking down organic matter underground in the soil and therefore away from direct sunlight. Contrarily that’s why all plants that use photosynthesis die when you restrict or remove them from light.

      Fungi’s use of glycolysis makes them much more similar to mammalian life forms that to plants. Since the human body already has tissues that normally produce energy via glycolysis, both aerobic and anerobic such as in short duration fast twitch muscles, the body doesn’t recognize certain systemic fungus as foreign invaders, and that’s also why systemic fungal infections are so virulent and often extremely hard to eradicate without killing the host human in the process.

      The Phase 1 anti fungal diet as advocated by Doug Kaufmann at Know The Cause dot com consists of a food elimination diet that removes foods that are commonly contaminated by various fungi and mycotoxins, and after eliminatiing those groups of foods you’re pretty much left with a paleo style fresh whole and natural foods diet, and that’s why both the Phase 1 and paleo diets work to eradicate systemin fungi.

  44. Interesting, I got breast cancer mid last year, had it cut out and then started eating primal. I declined other treatments and have started fasting until about lunch almost daily. I feel better than I ever have my weight is right down and the cancer is still gone 🙂

  45. There is a natural cure for cancer that was discovered in 1930. It’s sulfur. I can’t seem to copy and paste the link while on my phone but if you google The Live Blood and Cellular Matrix Study there is a great article on ecognitive about sulfur, it’s role in bringing oxygen into the cells and how cancer is anaerobic. My daughter and I have been primal for two years and have been taking sulfur for over a year. She was autistic but the sulfur helped her to talk again after being nonverbal for nine months. I’m not saying sulfur is a miracle but hot damn that stuff works.

  46. We had a really nasty respiratory bug floating around the nursing home I work at about two months ago–half the residents got sick and almost all of the therapy staff contracted it at some point. I did 16-18 hour intermittent fasts during this time and although I did get sick, it only lasted for about 5 days with more mild symptoms, as opposed to everyone else who was sick for 3-4 weeks. Considering I have been very suseptible to respiratory infections in the past, I should have been sick longer than anyone else. I attribute this shortened duration and intensity to fasting and eating Primally.

  47. There’s another quote attributed to Prophet Mohammed: “Fast and be healthy”.

    I have been suffering from psoriasis since the age of 17 (I am now 43). Every Ramadhan when I fast for about 15 hours a day for 30 days straight, my skin clears up remarkably.

    1. There’s a newer quote from the prophet Dr. William Davis from wheatbellyblog dot com: “The modern mutant wheat that only grows 2 foot tall ain’t your grandmother’s wheat.”

      And from prophet conrack: “Get a clue, drop wheat & grains totally & permanently from your diet and be done with your suffering from psoriasis once and for all.”

  48. Last time I got a stomach bug (barfing and shitting yourself) I fasted and beat it within 12 hours of experiencing my first symptoms; didn’t eat for two days because my body told me not to, but my energy was perfectly stable until my appetite came back.
    A few co-workers also caught the same bug, none of them recovered any faster than 3 days after experiencing their first symptoms because they kept eating and feeding it, whereas I starved it out and recovered within the first day.
    Cut off the food supply for a bacterium, yeast or whatever it is and soon enough it’ll die off from lack of energy and the competition from your own team of bacteria and immune cells.

  49. Fasting is a great tool to health. Everyone should at least read up on it if they haven’t yet.

    Now for a little math: If one was to fast one day every week, then that would be 52 days a year. That is almost two full months of not eating.

    If nothing else, it’s a great way to save money! But it is so much more!

  50. I fasted at true north heath center in california..I felt a lot better.I am sure it will clean you body of toxins so that they won’t react further and cause cancer later

  51. I drink Yerba Mate every working morning. Oftentimes I do not have any breakfast, which effectively means a 14 hour period without munching anything.

    Does this count as fasting?

  52. I have chronic myeloid leukemia,CML. I was eating “mostly” paleo before diagnosis in July but more strict now. I don’t do chemotherapy but take an oral cancer drug once a day. I love this article but wonder how it would work on a blood cancer. When we start our cancer drugs the Stem cell that caused our cancer goes into hiding and hibernation. We can be PCRu, leukemic cells undetected in a sample of blood, but we are never in remission or cured. That stem cell is still hiding in there somewhere.

  53. love all the comments and totally agree that on fasting days I feel full of life and joy and razor sharp
    if I get tempted to eat something its only because of my mind talk – the body and soul doing just fine
    so it is best for me to stay away from the kitchen
    thank you all for the encouraging messages here, so great to know Iam not alone-fast day today!

  54. Well this is very interesting. I had being trying to lose weight for months late last year and was pretty much on a low GI diet but wasn’t really shifting the weight like 3 yrs before. It was very upsetting and confusing. I was 100% PRIMAL back when it fell off, age 49 at a rate of 1 kg a week. Now I am menopausal, not sleeping, stressed and only just getting some walking and primal exercise back into my life. I realised after discovering this place that I was not 100% Primal this time around. Also pretty much sedentary for the past 2 yrs no longer walking 35min each day before dinner due to my new office job and weird working hours.
    Looking back 3 yrs ago, I remember how effortless primal eating had been and how I lost interest in carbs to the point that not one touched my lips in 12 weeks. Wow. now I know why.

    I have been Consciously Primal since early Jan when I discovered this wonderful place in my frustrated attempts to understand what was stopping me from losing weight this time around. Watching my family dropping about 5 kg in 7 weeks whilst I lost only a 2 and then hit a plateau was tough.
    Recently I wanted to find out more about the hard science behind weight loss and i have just read Primal Blueprint plus Good calories Bad calories and Why we get fat by Gary Taubes. Wow that satisfied my need to know the details.
    Sleeping is a major problem. I am taking valerian and magnesium complex and woke up twice last night instead of every 90 minutes. Here’s hoping the Valerian will help me out of this 2 yr horrendous sleeping pattern. I’ll keep you posted.

    So here’s the thing. I read about fasting here and I became a little worried that if i fasted i would ruin everything by slowing my metabolism down and needing even less primal calories to sustain my weary menopausal bod. I managed an easy 24hr fast last week and was thinking of stepping it up to 7 day fast. I am no stranger to fasting. I did religious fasts as a kid, about 3, 7 day juice fasts in my 20’s and about 3 in my early 40’s losing around 9 lbs each time. Living in Eygpt in my 31st year I tried a 30 day Ramadan fast and ended up doing 4 in the following years. What really surprised me about Ramadan was that i thought i couldn’t do a 16 hr water and food fast because i had lots of issues with blood sugar and hypoglycemia but actually even though i ate carbs in those days, my blood sugar settled down during the fasting month to my absolute surprise. Now that i have ready Gary’s books and loads of articles here I realise that its been insulin all along. Stop the flow of insulin and i turn into a happy chappy.

    Do you think it would be unwise for me in particular to do a long fast to kick start the fat burning and keep it going?? Could it mess things up and cause my body to hang onto more fat since I am sleep deprived and not functioning metabolically like most other folks.. I really want to lose weight… help!!!!

  55. Anyone have any experience on fasting results for “hard gainers” like myself? I’m 6’5″ and 170lbs, skinny as a rail. I went primal a few months ago and love it for the usual reasons, energy, no shakiness when I miss a meal, hunger management, less muscle soreness after workouts. But I am someone who has to work ridiculously hard to PUT ON weight. So would IF have any benefits for me?

  56. Mark–nothing to add to your points. It’s hard to find a reason NOT to fast. A lot of my family are naysaysers. Pity that the “breakfast is the most important meal” and “several small meals” has been pushed so heavily that people can’t consider fasting.

    Here is a quote from Mark Twain that I think applies to your post:

    “A little starvation can really do more for the average sick man than can the best medicines and the best doctors. I do not mean a restricted diet; I mean total abstinence from food for one or two days. I speak from experience; starvation has been my cold and fever doctor for 15 years, and has accomplished a cure in all instances”.

  57. haha I on the leangain fasting. It great to know that marks in to fasting to. And if people think you lose muscle check out the web site leangains.

  58. anyone breastfeed and fast? i don’t want to ruin my milk supply or get mastitis.

  59. Mark, I began incorporating intermittent fasting into my life in January of this year as a way to lean out and jump start weight loss after gaining a few holiday pounds. I fasted for 16 hours each day following the guidance at leangains.com. I wrote 3 blogs about the “experiment” as I called it on my blog. http://www.summer-smith.com. The experiment was so successful and I felt so great that I have continued to follow the plan 5 to 6 days per week. I am an avid believer in this practice and want to find ways to incorporate periodic, longer fasts. Great write up on the benefits of IF as it relates to cancer treatment. If it can do that for cancer treatment, imagine the benefits of IF for cancer prevention!

  60. For some reason my comment didn’t post, so I will remove all the links — maybe that was the problem? — anyhow…

    What I have found on fasting and/or caloric intake restriction agrees with your’ research, here, Mark, but you missed a thing or too (see entry #9 at bottom), and while my research showed affects on life-span, I infer that anti-cancer benefits also emerge:

    (#1.) “These results suggest that total caloric intake may modulate the rates of cell death and proliferation in a direction consistent with a cancer-protective effect in DR mice and a cancer-promoting effect in AL mice.”

    (#2.) “9. Weindruch, R. and Sohal, R. S. (1997) Caloric intake and aging. N. Engl. J. Med. 337, 986-994.”

    (#3.) “13.Dhahbi, J.M., Tillman, J.B., Cao, S., Mote, P,L., Walford, R.L., and Spindler, S.R.: Caloric intake alters the efficiency of catalase mRNA translation in the liver of old female mice. J. Gerontol. 53A: B180-185, 1998.”

    (#4.) “A UCR researcher finds a connection between decreased caloric intake and increased life span.”

    (#5.) “We have known for many years that reduction of caloric intake by up to 40% over that of the normally fed diet, while also maintaining essential nutrients and avoiding malnutrition, is the only intervention that will extend the maximum life span of animals from many different genera.”

    (#6.) “Caloric Restriction, or reducing the caloric intake by 30 to 50 percent, has increased both the average and maximum lifespan in rats and mice more than 30 percent. The animals receive enough nutrients but weigh considerably less than their non-restricted counterparts. Studies have also shown that the rodents are healthier, with lower blood pressure and a postponement of age-related declines in muscle mass, immunity and other areas.”

    (#7.) “Recent Research Shows Lower Calorie Diets are Associated with Longer Life”

    (#8.) “Harman: It was first shown in the mid-1930s that reducing caloric intake would increase both the average and maximum life spans and decrease disease incidence. I believe that this result was due to decreased free radical damage owing to decreased oxygen utilization. Glycosylation may play a minor role in this effect as glucose levels go down when calories are restricted.”

    (#9) Researcher, Gordon Wayne Watts, BS Biological and Chemical Sciences (FSU, 2000) thinks that the reason reducing caloric intake helps increase life span is quite simple: When the human body is not overloaded with food, it can more easily get rid of bodily waste products –and thus, we have the body’s cells able to reproduce and heal in a cleaner chemical environment.

  61. Ok, inspired by Mark’s post I did a 2 day fast. I only drank green or black tea without anything but water. I lost two pounds. I am a very stubborn weight loser (down to those A receptors I guess) so this was fun to see. It was quite easy actually and I am thinking of doing it bi-monthly. Not sure if this is typical protocal however I broke my fast with a Scotch whiskey. I highly recommend not eating for 48 hours then having a shot of whiskey and waiting about 15 minutes. It was a wonderful buzz. It also seemed to take a bit off the need to devour that first meal. For my breaking-the-fast meal I had a nice big salad, some squash with butter and a half rack of ribs and I was full. When I woke up in the morning the 2 pounds I lost were still lost. (I hope I never find them) I broke my fast while watching “Gandhi” which, even though he’s one of my true inspirations, gave me some strange perverse and ironic joy, especially since I broke my fast eating ribs.

  62. Thank you so much for the very illuminating post Mark.

    After reading your post and the numerous ensuing comments, I’m starting to wonder whether we should put all the different kinds of intermittent fasting into the same category –“IF”. I’m not quite sure that a fast lasting several days (even 24hrs) has the same effect on the body as a fast done for 10hrs only within the day. I guess fasting for several days is something one can do occasionally, whereas fasting for 8-10hrs is something that can be done everyday.

    For instance, I’m used to fast from the early morning till the evening, and have my main (unlimited 😉 ) meal of the day at dinner. That’s my routine and I’ve been following it naturally (without any pain) for years. Actually I feel stronger and more productive during the day when I’m fasting. However I’ve never tried any form of long fasting, and I can imagine my body may react differently to it.

    I would be very interested in knowing whether the effects of both kinds of IF are comparable (in terms of all the advantages mentioned concerning the metabolism etc.)

    Thanks in advance for your insights!

  63. I’ve always been of the mind not to eat, or majorly restrict consumption, while ill. I don’t currently make intermittent fasting a habit, but this has given me a lot to consider about it. I may also discuss it with a friend who is about to undergo chemotherapy treatments, although he’s not primal, very conventional wisdom, so I’m not sure how far that will get.

  64. I had read Mark’s first article about fasting and was floored. It really was ok to skip a meal if I was not hungry!
    Since that day I have only eaten one meal a day…happily!
    What freedom!
    I have a nice new clarity of mind, I have slept like a champ, and I feel so good inside.
    Now to read this might help keep me from cancer…bonus!!
    I have so much to thank Mark for…we all do…
    Please keep up the good research for us.
    I appreciate you and your work.

  65. Mark,

    Good read, thank you! I’ll be forwarding this to my brother-in-law, his mom has breast cancer. I try and fast twice a week, one shorter, say around 12-16 hours and one dedicated full 24 hour fast a week. I do my 24 hour fast on my recovery day so my training doesn’t suffer. Just got done reading “Primal body primal mind” by Nora Gedgaudas, she’s got some good info on fasting and the positive physiological effects of it.

    Looking forward to your next post!


  66. Does anyone think fasting might help the auto immune condition scleroderma?

  67. With three generations of cancer occurrences (some minor, others severe)in my lineage, I am more aware of the nature of the impact than some of my peers. Fasting, for me, has previously only been about sleeping through part of it and then skipping breakfast and lunch. I am at a plateau with fat loss at the moment, so I’ll step up and add another meal… er.. subtract one more and see… I love this site so much. I can honestly say it changed my life in the last 6 months.

  68. Hi all! I would like to add an appendix to Mark’s notes about who shouldn’t be fasting. I’ve done a fair bit of research into the neurobiology of fasting, and I’ve posted a summary of it, titoled Hypocretin Neurons: The Link Between Fasting, Stress, and Arousal, or, Why Fasting Breeds Insomniacs, here: https://www.paleoforwomen.com/hypocretin-neurons-the-link-between-fasting-stress-and-arousal-or-why-fasting-breeds-insomniacs/

    Not self promoting, just wanting to get the news out there. Fasting goes wrong for many people, and I think its helpful for them to understand why

  69. I enjoyed reading your site, and just wanted to pay you a compliment: You’re a pretty good writer.

  70. Thank you for taking the time to make this article. As a Muslim what I want to say is: Just be Muslim. It is mandatory in Islam (except for women with menses, children, and for those who can fast with difficulty, ex:old man) to fast from sunrise to sunset for a period of a month (Ramadan).

    Additionally, it is advised in this religion to fast Mondays and Thursdays.

    Thank you for your article.

  71. I actually have stage 4 breast cancer and have had incredibly good results lately following a paleo diet and supplement program designed by my holistic doctor (as well as with chemo and radiation.) For the first time in a year in a half, my scans have come back with results of all the lesions in my lungs and liver shrinking considerably. I have just taken up intermittent fasting as of yesterday because I have read about it’s effectiveness when used in conjunction with chemotherapy. I have treatment tomorrow morning and I plan on fasting from 9pm to 1pm. I’ve done it the past two days with no ill side effects, in fact, I feel great while fasting… very focused and alert!

  72. I have had ulcerative colitis for over 20 years. Even before that I had happended to read a book called something like “Triumph Over Disease by Fasting and Natural Diet” by Jack Goldstein (written in 1970’s). It basically outlined his personal experience of being cured of colon disease when he was at the point of death through a pronglonged (42 day!) fast at a fasting and healing center. I kept this in my mind but never fasted for more than the occasional day, UNTIL a colonoscopy revealed to me that I *might* have colon cancer 2 years ago. My gastroenteroligist wanted me to have my colon taken out, but first he scheduled a second colonscopy where he was going to take many more tissue samples from my colon. The shock of possible cancer woke me up and I immediately fasted (while continuing to work) for about 9 days, followed by intermittent fasting for 3 more weeks. I probably consumed nor more than 5 “regular” days of food in 30 days. At the second colonoscopy the doctor took over 100 biopsies, none of which tested positive for cancer or even “pre-cancerous”. Did the fasting help? I am not sure. I have fasted the occasional day or two since then, with 5-6 days max, but sometimes find it hard to start these now because I keep thinking i really need to fast to “weeks”. I sometimes eat well, sometimes bad for stretches. 2 years later I need to go back in for another colonoscopy. I know if it finds any cancer I will turn to fasting before or in addition to any chemotherapy treatments.

  73. Wow, just wow, fasting just keep on rolling out the benefits! My husband and I just started the fasting lifestyle (one meal a day). We have our reasons for fasting, mine was originally only to lose some weight, but as time goes by and after all the information I have read here and on other sites, I really feel so committed to this lifestyle for so many more reasons. It just simply makes sense to me.

    The cancer research is so interesting to me and obviously wonderful. We were just discussing cancer yesterday, because so many of your friend’s parents are finding out that they have cancer and basically, it’s just really scary. I almost feel that nowadays you are lucky if you don’t get cancer. My only problem is this; people are suborn, they have been told all their lives that ‘not eating=bad’, how on earth do you convince the people you love to change their mind set about food? We basically keep our eating habits a secret at this time, I tried to tell one of my friends what we are doing, but my word fell on deaf ears once I mentioned that we were only eating once a day!

  74. A great article. Everyone has different meaning of the word ‘fasting’, but I would suggest to use the one that Muslims use. They have been fasting for nearly 1500 years and billions of them, so try it out. Fasting to them means nothing to eat or drink from dawn to dusk!!! When you finally eat, eat in moderation. The prophetic way was to eat less, and when eating, eat one type of food at a time. Simple food is preferable to complicated food. Of course stay far from processed foods, sugars, table salt (use Himalayan rock salt, or at least the good quality sea salt). Use olive oil, dates, figs, cinnamon, turmeric, pomegranates, apples, vinegar, tomatoes (cooked), cocoa powder, honey, lemon, lots of fruits and vegetables, and daily exercise. You are then good to go!!!

  75. Great explanation of the benefits of fasting! I’m one of Valter Longo’s researchers, so I love to see people outside of the lab really understand and apply his findings to their every day life!!

  76. Having just finished five months of chemo, I can attest to the correspondence between IF and treatment results. Currently I have been in a prolonged “fast” of about 7 weeks. Only when I speak of it to others do I refer to it as “fasting,” because indeed this is what it is; however, in practice it’s listening and respecting my body’s cues. My body tells me when to eat meat or fruit or simply nothing but water or juice.

    And I am conducting voracious research to boost my immunity and reduce inflammation by treating food like medicine. From the outside looking in, it can be called “fasting.”

    My husband scoffs and says, “You’re not ‘fasting’, you just don’t eat!” This is it EXACTLY.

    I think IF is a bit like semantics and more like a way of life to promote healing, not from research (1st article I’ve encountered), but from experience and by respecting my body.

    I think I got here by ignoring my body’s intuition, so now it’s game on and cancer’s going down!

  77. I read an incredible story of how two men beat their bladder cancer by water only fasting. It truly is amazing what the body can do with just water. I’m glad you included the human trials in your article in really shows credence to the topic of water fasting and cancer. Great article as always.

  78. Hi,

    The soviets did experiment therapeutic water fasting since 1960. They have thousands of pages of scientific measurement about it. It’s public, but unfortunately in russian. There are “fasting clinics” out there since the 70’s.

    Also was later independently developed int germany some form of therapeutic fasting:

    The Russians followed your reasoning about that: some patient refused to eat in a psychiatric hospital? so let them fast, instinct will prevent them from dying of starvation. Then they realized that some healed from fasting!!!! And there began their experiments.
    I saw a very good documentary on the franco-german channel “Arte” about that. So if you speak either language…

    1. Thanks a lot for mentioning this! I do speak french and I’d like to watch the Arte documentary you’ve referred to, but I could not see it on their site:


      Do you remember the name of the documentary by any chance?

  79. As a treatment for colon cancer I began a ketogenic diet (no more than 30g of carbs/day, a normal amount of protein, and plenty of good fats) three months ago. After two months on the diet (during which time I had no chemo) I shot completely negative on a PET Scan for the first time in over two years. It does not take long for these glucose deprivation diet approaches to work. I was not overweight when I started the diet, and my weight loss leveled off at twelve pounds. I feel great, and my blood tests have been fine. It’s important to make sure to get enough good fats, such as those found in olive oil, flaxseed oil, and nuts, and cheating, by the way, is completely out on this diet. Some exercise each day should also be a part of the mix. If you’re using this diet to fight cancer, it’s also worth it to check out the “anti-inflammatory” diet, which can be easily implemented together with the ketogenic diet. Don’t wait for your doctor to suggest these types of measures. We have to research these things ourselves..

  80. I have RA and had my first bad flare a couple of weeks ago. Everything hurt…even turning my head hurt, I couldn’t make a fist or move my hands feet, wrists, ankles or knees much at all. I immediately began a water and herbal tea fast and by day three I could move freely! I continued for a total of seven days. It is certainly healing! Then I started the Paleo diet. So far so good! Thanks for all the good info on here!

  81. I am 36. My first fast in my life was this summer. I like to do things properly so I read a few books to prepare and I fasted for 3 weeks just on water, then for another 3 weeks I slowly introduced food to my body again. It changed me, I want to do it again next summer 🙂 It was very hard but was worth it since it made my body get rid of the daily headaches I used to have and the constant constipation. One thing I couldn’t get rid of though is my bloating :(, I continue get very bloated after every meal and feel not sharp but almost constant lower left abdominal pain. Hopefully will get this fixed with the next fast. Fasting becomes easier after the first 2-3 days and drink a lot of water even if you are not thirsty! Any kind of food you consume meanwhile makes it not a real curing water fast so forget the supplements and the drinks. Good luck!

  82. cannabis oil but it did not work.It was faithful day i was in the hospital to do my normal check up then on my way home i was on a discussion with a friend i met on the walk way she then ask me how was my family and what brought me to the hospital i then told her every thing with tears on my eyes and she was touched and she told me she could be of help to me that there is this Doctor that has a very good and active cannabis that has the power to cure every cancer,she then further told me that she had cancer on her leg some times ago that it was Dr.AISHA ADAM cannabis oil that brought her back to life and she don’t feel any pain again,she gave me Dr.AISHA ADAM contact ([email protected]) i contacted him and after some little stress it was was delivered to me in my country USA in less than five days.To cut my story short i applied it as he explained and glory be to God today i am completely healed by Dr.AISHA ADAM cannabis oil and i am glad to let the whole world know this good man and contact him for help through his email([email protected]) calling number 2348148345303

  83. What about fruit?, I suggest looking up Robert Morse ND. A raw vegan diet along with fasting has cured all my symptoms.

  84. Cancer has motivated me to fast. I’m 20 days into my first water fast. Prior to which I did several 24 and 48 hour fasts to ease the transition. After discovering research on the effects of fasting on tumor growth I decided I’ve nothing to lose at this point if I try. Five years ago I was diagnosed with endometrial cancer and given 12-18 months to live. It quickly grew from the size of a grapefruit, to a cantaloupe and as of my last scan, a watermelon. Although radiation was encouraged by one physician, neither chemo or radiation were effective options. A total hysterectomy was not recommended because my overall health has been so compromised. I’m grateful for all the research on fasting and hope IF fasting allows me more time to celebrate life.

    1. Thena, how did it go? Did you have success with the water fast? My girlfriend was diagnosed with endometrial cancer and has just started juice fasting with the Breuss system.

      1. Stefan, I just discovered your reply. Well, I’m still here Stefan. Although I didn’t find fasting difficult, I will say that ending my fast could’ve went better. I should’ve eased back into solids with green juices, then perhaps melons, etc. I believe cutting refined carbs from my diet combined with intermittent fasting and periodic water fasts have helped. Stefan, I wish I could tell you my cancer is eradicated, however I am happy to have quality of life. If you’re interested, I recommend checking out a few doctors on the subject: Dr. Jason Fung, Dr. Thomas Seyfried and Dr. Vincent Longo. Also, a helpful website regarding alternative therapies is “cancertutor.com”. If your wife is on a juicing protocol similar to Gerson’s and is diligent and patient, she may prolong her life. Still, I tend to think it is not so much we eat or drink as it is what we’re not consuming. Sugar is cancer’s best friend. When you fast, your body will go into autophagy, but even the slightest amount of protein will throw you out of apoptosis. There’s interesting research regarding regulating Mtor. My heart goes out to you. I’m praying for her.?

  85. Does anyone have any opinion on the calorie intake on non fasting days? I’m fasting for 72hrs but worried about weight loss – should I make up the missed calories over the rest of the week?

  86. After round three of chemo, I’ve just not gotten back to eating- would try and just got nausea and vomiting. I was already morbidly obese and had lost some 20 pounds before I started chemo. I’ve always been super sensitive to smell and taste, so that seems to be contributing to lack of desire to eat. I know our Creator set these body systems in place, to use fasting for healing. The biggest issue now is seeming lack of support from family. I guess it alarms them that I am not the “fat one” and they feel they must restore me back to where I was? I’ve lost over 50 pounds from the heaviest that I was before I was diagnosed with breast cancer (late 50’s caucasian female.).

    So we’ll see how this rides out…

  87. I’m a 39 year old women who was diagnosed with breast cancer two years ago. I wish I had read this when I was going through chemotherapy, I feel it would’ve been quite helpful. I’ve starting IF and have even completed some longer fasts of two and three days. My question what is the optimal fasting time for cell autophagy for prevention of a re-occurrence of cancer and how often is it recommended

  88. Dear Mark,
    I just read your article on fasting and cancer. I’ve been diagnosed with stage 4 lung cancer. I’ve been put on Tagrisso 80 mg every other day. I am also seeing an energy therapist and trying to modify my thinking and beliefs. Ive improved greatly. The modules and tumor has shrunk.
    There were times in the beginning where I craved beans, legumes and dandelion greens. It’s been a year and my cravings have leveled off and my healing seems to have phase hit a plateau. Maybe I’ll try fasting. My primary told me to eat small meals 6 x per day.
    What are your thoughts?

  89. This research, this method of using ketosis in the treatment of illness and especially cancer is the way of the future. We should all do intermittent hard dry fasting for improved health.