Dear Mark: Strong but Stiff, Denatured Proteins, Weeklong Fasting, and Oxalates

Back PainToday’s edition of Dear Mark is a bit of a grab-bag. First, I give advice on how to loosen up after strength training. Being able to deadlift however many pounds is nice and all, but what if you’re too stiff on your days off to do anything with the strength? Next, I briefly discuss the effect of heat on protein powder and raw cocoa powder. Raw fans will try to scare you away from anything heated, but are they exaggerating (or outright getting it wrong)? Find out below. After that, I sort of try to convince a reader not to embark on his planned week-long fast. Or, at the very least, to reconsider the week duration and try something a little shorter first. And finally, I discuss whether or not dietary oxalates are a toxic substance that should be avoided at all costs.

Let’s go:

Dear Mark,

I go to the gym three times a week and lift weights. Once a week in addition I do some sprinting on the treadmill, and once a week I do a high-intensity bodyweight workout. After many of my workouts I feel very stiff the next day. What can I do about this? Is it worth it to build up my strength if I’m so stiff I can’t do anything with it?



No, I don’t think strength is worth very much if you’re hobbling around stiff-legged all day, too sore and functionally decrepit to translate that added “strength” into kinetic energy. Since you wrote in about this, you probably feel similarly. It’s a common intuition to have.

Luckily, there’s a simple fix that doesn’t require you stop exercising, or even cut back much: mobilize.

Start your day with a brief but effective movement session. I highly recommend drawing on this VitaMove routine by Angelo dela Cruz, PrimalCon presenter, bodyworker, and ninja warrior, for inspiration.

As Angelo says, rather than dynamic, be fluid and thorough. Don’t use momentum to throw your body parts around time and space. Seek full range of motion with every movement. Be deliberate, even slow. When you squat, for example, bend at the waist, grab your toes until your hamstrings stretch, and pull yourself down as deep as you can. Oscillate back and forth, shifting weight between your feet and really feeling the stretch in your thighs. Extend your arms overhead and stand up, squeezing your glutes and bringing your hips to full extension at the top as you stand.

My favorite hip opener when I’m short on time is the walking lunge stretch. Take a big forward step as you lunge, back knee hovering above the floor. Hold that position, extend your arms out in front, and place your palms against each other. Keeping your arms straight, move them as far to the left as you can, then as far to the right, then repeat it. Think big, sweeping, expansive movement; you should feel your fascia stretching. Lunge forward with the next foot and repeat the arm movements. Experiment with different arm movements, like chopping motions.

On your off days, go for a walk. Do about an hour, if you can. Keep those joints fluid and moving.

Also, consider dropping one of the weight lifting or bodyweight days. I think three days of strength training plus a day of sprints is plenty.

I’ve made homemade protein bars using both whey and egg white protein powders. Does baking these have any adverse effect on the nutrition or protein content? I also have a raw cocoa powder that I use in a few different things, but I also use when I make these baked bars – any issue with heating raw cocoa powder?


If heating protein resulted in an inability of the hominid digestive system to access and assimilate said protein, I don’t think we would have gotten very far as meat-eating, fire-starting, barbecuing apes. Raw foodists will talk about heating resulting in “denatured proteins” as if they’re a bad thing (and I gotta admit, they do sound kinda scary), and that’s all well and good, but denatured proteins are generally more digestible than undenatured proteins. We’re always denaturing the proteins we eat before we eat them. When we cook egg whites, the proteins become denatured and more digestible. When you stick seafood in a lime juice bath to make ceviche, you’re denaturing the proteins. That doesn’t “destroy” the proteins; it just rearranges them. They’re still broken down in the gut into amino acids.

The confusion may arise from the fact that denaturing proteins in living tissue (like, say, you) often causes cell death. Denaturation of living protein, bad. Denaturation of dead protein that you’re about to eat, good. If anything, baking your protein powder will make them more available in the body, rather than less. And besides: most whey proteins have already undergone a heating process. You’re in the clear.

As for the cocoa powder, I wouldn’t worry about heating it, either. For one, some of the earliest cocoa fans – the Mayans – consumed it roasted, not raw. And second, the roasting process actually increases the antioxidant activity of the cocoa bean. All those cocoa polyphenols we’re so interested in are actually boosted by heat. It seems the Mayans got that one right. Furthermore, many supposedly “raw” cocoa powders undergo plenty of heat stress, whether it’s during the crushing process or because there’s little consensus on what “raw” actually means.

I am considering attempting a week long fast. I have been fasting intermittently for some time now, and thought it would be a cool challenge to go an entire week. As a fat adapted “caveman” should I worry much about muscle loss, or any other potential problems for that matter?


Amino acid scavenging from existing stores will start to happen when your liver glycogen is depleted, which will occur at somewhere around the 24-30 hour mark (depending on a number of factors, including your activity level during the fast). Any dietary protein available will go toward gluconeogenesis and liver glycogen replenishment. After that’s all used up, you’ll draw on your own tissues – probably less so than the average person thrown into a week-long fast, given your ability to use fat and spare glucose, but muscle loss will still occur. A week is a long time.

Short term fasts with refeeds generally prevent any metabolic slowdowns, but a week-long fast will put your body on alert. Thyroid activity will downregulate and leptin will drop. By all accounts, you’ll officially be in “starvation mode.” This will be highly unpleasant.

In my fasting series, I wrote about how severely obese patients have had success with year-long fasts, but they were under medical supervision and had a lot of extraneous tissue to burn through. I take it that you do not, so I would advise against a weeklong fast. If you insist on pushing the limits (can’t blame you there), start smaller. Try a day-and-a-half long fast, first, and see how you respond. Go from there, and stay cognizant and realistic about how you’re feeling during the fast. Be willing to cut it short if you feel terrible.


I just wanted to ask you to add to your Primal Blueprint a warning of the dangers of oxalic acid. We hear we need to eat a lot of plant food, like dark, leafy greens. Oxalic acid in many fruits, vegetables, nuts and berries can cause kidney problems and even death. I would like you to share with the public that we should be aware of foods high in oxalic acid, not eat the same plant foods regularly, and not consume too much of it. It doesn’t take much oxalic acid and it doesn’t need to be over a long period of time, before you might get ill from oxalic acid! It’s highly toxic! There should be a warning to people about this, especially when they choose to eat Primal! (And this is why I think we were born with a sweet tooth! To avoid plant food that are high in oxalic acid!)

Best regards,


I don’t know that I’d characterize oxalic as “highly toxic,” at least not unequivocally for everyone.

In healthy guts, oxalates will generally pass through the GI tract into the stool without being absorbed and causing problems. Just between 2-15% of dietary oxalates ever get absorbed in healthy people, depending on the inherent solubility of the oxalates (almond oxalates, for example, are more absorbable than black bean oxalates). In compromised guts, oxalates will be absorbed at greater rates. People with celiac disease, which is usually characterized by a perpetually permeable gut lining if left untreated with a gluten-free diet, are at a higher risk of calcium oxalate kidney stones due to (in part) greater oxalate absorption. Certain species of gut flora also contribute to oxalate degradation (PDF), so individuals without the right species will experience impaired oxalate breakdown, leaving more oxalate available for absorption. Probiotic supplementation with the right species has been shown to reduce urinary excretion of oxalates and the formation of stones in patients with hyperoxaluria.

When oxalate is absorbed, however, the vast majority of it is excreted through the urine. Too high a concentration of urinary oxalate can lead to impaired dissolution of oxalate and the formation of kidney stones; less oxalate in the urine by volume means the oxalate is easier to dissolve.

Some people definitely have problems with oxalates, either because of intestinal permeability, hyperoxaluria (excessive urinary excretion of oxalate caused by impaired oxalate degradation enzymes and/or increased oxalate absorption), or dysfunctional gut flora. Those people will want to limit oxalates and cook their greens. Other strategies include taking a calcium citrate supplement with meals (calcium citrate binds to oxalate in the gut and reduces its absorption), taking a magnesium-potassium citrate supplement, and supplementing with probiotics.

The benefits of “high oxalate” foods like leafy greens, nuts, and other vegetables are such that I wouldn’t give up every oxalate-containing food. If you’re worried about oxalates, rotating the greens you eat (kale and collards are some of the lower-oxalate greens) and limiting the amount of raw vegetables you eat should reduce your oxalate absorption.

If you do have leaky gut, celiac, any intestinal disorder like Crohn’s or IBS, generally poor digestion, or have a family/personal history of kidney stones, check out Low Oxalate Info, a handy, comprehensive website dedicated to low-oxalate living.

That’s it for today, folks. Thanks for the questions and keep them coming!

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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76 thoughts on “Dear Mark: Strong but Stiff, Denatured Proteins, Weeklong Fasting, and Oxalates”

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  1. A week long fast seems like it would be pretty intense. I slowly built up to being able to do a 48 hour fast. I considered going longer but I was really worried about losing muscle. With a 48 hour fast I didn’t lose any strength the next time I lifted.

    1. Yeah I wouldn’t recommend a week long fast for an athlete. But 48h is my sweet spot for purging after holiday feasts. I always find the second 24 hours is easier than the first. Probably from super low insulin and just being adjusted to the idea that I won’t be eating that day.

      1. Leangains sited a study that showed muscle catabolism did not start to occur at seriously until about the 72 hour mark. The 24-48 hour fast seems to be a good occasional break for most people.

    2. I started doing IM about 6 months ago, after resisting the idea for a couple years. It has really benefited me, especially in fat loss.

      Can one of you explain the benefits I would get from a 48 hour fast?

      1. It gives your digestive tract a rest and allows you to burn a lot of fat (if you need to do that). It also improves your insulin sensitivity and reduces your risk of cancer.

    3. I’m sure its been discussed here before, but how often and how long should fasts be? I know I’ve read a few comments about 16 hr fasts and 48 hour fasts. How often do you do a 16 and how often a 48?

    1. The point of consuming undenatured protein is to boost your glutathione levels. All protein is good for you and cooking the majority of your protein is OK. But, having some raw undenatured protein in your diet is a great idea. The best source is cold-filtered whey.

  2. Oxalic acid. If anyone at a wedding dares you to eat the Calla lilies, chicken out. Not that I know from experience, but I’ve heard it makes your throat swell and feel like you ingested large shards of broken glass. Just sayin.

      1. ok, that was pretty animanarchic. Isn’t there a little Animanarchy in us all?

        1. Converts? An internet-personality based adjective? Takin’ over the world Pinky.

  3. Raw cocoa is most likely a misnomer. The chocolate taste is developed from the roasting of the beans, and to top it off, the way that cocoa beans are fermented (on the ground in third world countries) makes me less than enthusiastic about raw cocoa beans. A local chocolatier was asked if by a lady if she could buy raw chocolate from him, so he took a truffle and rolled it across the ground, then asked her if thats what she wanted to eat. That was his less than subtle metaphor of what you would get from raw chocolate.

    1. Yes, it is possible. In fact, it was done 40 years ago at the University of Dundee in Scotland. The man went on a 382 day fast and lost over 270 pounds.

      Of course, it dosen’t look like you could go that long, nor should you try it. The gentleman in the study had constant medical supervision.

      Here is the summary of the study (you can look up any additional information you require): A 27-year-old male patient fasted under supervision
      for 382 days and has subsequently maintained his
      normal weight. Blood glucose concentrations around
      30 mg/100 ml were recorded consistently during the
      last 8 months, although the patient was ambulant and
      attending as an out-patient. Responses to glucose and
      tolbutamide tolerance tests remained normal. The
      hyperglycaemic response to glucagon was reduced and
      latterly absent, but promptly returned to normal during
      carbohydrate refeeding. After an initial decrease was
      corrected, plasma potassium levels remained normal
      without supplementation. A temporary period of
      hypercalcaemia occurred towards the end of the fast.
      Decreased plasma magnesium concentrations were a
      consistent feature from the first month onwards. After
      100 days of fasting there was a marked and persistent
      increase in the excretion of urinary cations and
      inorganic phosphate, which until then had been minimal.
      These increases may be due to dissolution of excessive
      soft tissue and skeletal mass. Prolonged fasting in this
      patient had no ill-effects.

  4. i tend to agree with CW which says fasts longer than 3 days can be dangerous and should not be undertaken without medical supervision. more, is not necessarily better. this goes for fasts too.

    1. I also agree with this. I no longer fast at all on purpose. If I fast at all it’s because there is literally no food around me at all or it’s literally pure junk. I may die any second so I want to feel great as often as I freaking can.

      One life – you better enjoy it!

      1. I agree, as a women I can say that years of sad dieting, low calories, low fat, ect… has wreaked havoc on most womens hormones, making it nearly impossible to loose weight even when fasting and eating paleo. I can go all day without eating anything and it really does not bother me, which I believe has put my body in a permanent starvation mode. I would like some more thoughts or input on that? Anyone?

        1. I think that when you practice a lot of nutrient deprivation, whether by fasting or calorie restriction, your body gets more effective at breaking itself down for energy and protein. You don’t feel as hungry, and you might not even see a shift in scale weight, but you will certainly be losing healthy mass.

          The solution in my opinion is to alternate periods of restriction with periods of surplus.

        2. Gary Taubes “Why We Get Fat” as some info about your question. Basically, if your metabolism gets screwed up (this can happen by unlucky genetics), it will support body fat rather than overall energy levels or your organs in periods of calorie restriction. There’s a very interesting study done of lab rats (yes, I know, not a good human analog) that were bred to be obese. When you restricted their calories, they stopped moving instead of losing fat. Eventually they died obese when they stopped feeding them altogether. Their genetics supported the fat instead of consuming it for survival. Even though rats are not good human analogies, the point is that study illustrates that non-healthy metabolisms do not respond to calorie restriction the way you’d expect.

          I’ve read that very carefully controlled high fat diets help people with metabolic disorders lose body fat (As opposed to weight – as Timothy rightly points out, weight can also mean cannibalizing muscle mass for glucose and nutrients.) Atkins has an extremely high fat diet in his book to start weight loss for the metabolically resistant and I think there are high fat floating around the net. I cannot attest to their safety, but if you’re struggling to lose body fat, you might want to know they exist.

        3. I tried Atkins 4 day fat fast. I was fine for 3 days but the 4th day made me feel terrible (weak/sick). Afterwards, I experienced sugar cravings and a reduction in exercise endurance.
          Now, I only fast for 36 hours and break my fast with meat and veggies. No more fast fads for me!

        4. If fasting dosen’t bother you, then you are hardly in starvation mode. Hormones, however, are responsible for weight gain and weight loss.

          If you are having trouble losing weight and you are eating well, it may very well be years of hormone imbalance that is responsible. However, what eating primally will do for you is keep you from gaining additional weight.

          So far as starvation is concerned, from a biological perspective, starvation is a long term stressor. Fasting as prescribed by most people is short in duration and a short term stressor. All biological life forms function well with short term stressors. In fact they thrive. An absence of these stressors is what causes a lot of the problems we have in society. Problems that are absent from cultures that have the short term stressors we lack.

          When you exercise and lift heavy things, thats a stressor on the body. Exercise too much, with too little recovery, and the stress becomes long term and the body begins to break down and lose its resiliency. Don’t exercise at all and you will atrophy. But, lift heavy things or what have you, and recover properly, and you will be stronger. The list goes on and on. Poisons, toxic things, bad bacteria…too much of these things will kill you. But small amounts will make your body more resilient to these things in the future.

          The human body was designed for these short term stressors. For instance, when fasting, the body will stop cellular growth and focus on cellular repair. It will also use as fuel the weakest proteins in the body first. It essentially uses this period to clean itself out. The human body was designed for small periods of eating very little…not a famine though, as you hear: “feast or famine”. A 150 pound person who is 10% body fat will have enough fat stores to last 3 or more. Too long of a fast and the long term stress will start killing you. But the short stresses of fasting will make you stronger.

        5. Hey! check out balanced bites podcasts, as they have some interesting points on women and fasting specifically. I also have a long history of unhealthy methods of weight loss, and eating paleo/primal has been the first time I am at ease around food I know is not good for me. When I have fasted, I tend to want those sugary, chemical laden food stuffs, and I have since quit fasting proprosefully for that reason. Maybe it is purely mental, but I try not to put myself in a position where I make poor choices anymore.

        6. I know what you mean. 3 decades of typical diets have left my body highly resistant to losing weight.

          I have been paleo for around 3 months and am starting to see changes, I recently starting doing a 24hr fast once a week. It really does seem to help – I have found that if I eat very low carb the day before the fast (high protein/high fat) then the fast is really easy and often I lose 1-2lbs in that 24hr period. And 2-3lbs overall in a week.

          Stick with it. I certainly feel better for eating this way, and the health benefits are translating into weightloss.

        7. Thanks for all the responses everyone! Looks like I have some reading to do. I have done low carb for years and converted over to paleo about a year ago. I have seen many changes that are positive but weight loss is not one of them. It is hard to be patient, after so many years of sad diets.

  5. “After many of my workouts I feel very stiff the next day. What can I do about this? Is it worth it to build up my strength if I’m so stiff I can’t do anything with it?”

    I wouldn’t trade flexibility for strength! Maybe you should try lighter weights, and focus on smooth, full-range-of-motion movements. And make sure you stretch thoroughly after every strength workout, even if it means cutting short the strength part of it.

    Flexibility allows us to move with speed, grace and efficiency (think of cats). Traditional Asian martial arts (and European fencing) emphasize suppleness and speed, both of which suffer if you become muscle-bound and bulky.

    You might want to consider taking a Tai Chi class once or twice a week.

    Good luck with the training, and let us know what works for you.

    1. Agree with Helga 100%.
      I like to have strength, but if I have to choose between suppleness and speed vs strength, I choose suppleness and speed.

  6. Last year did a 10 day filtered water fast to determine food allergens and it went very well. Your ability to focus intensifies as the mind forgets about constant food search and cravings. Starts becoming a bit spirtitual after just a few days.

    1. Do I want to know how you determine food allergens when drinking only water? 😉

  7. The longest I did has been a 30 hours fasting (I am around 10-11% BF, my purpose was to boost HGH levels). In these 30 hours I did two intense but short workouts (30-35 minutes circa), the second being just as full of energy as the first. However, needless to say, the fast break dinner has been a meat feast 🙂
    That happened only once. Now I do 24 hours maximum (dinner to dinner) and I do it very very rarely.

  8. I disagree that we are “born with a sweet tooth.” This is an old wives tale. Sweets are an acquired taste like any other flavor. Unfortunately, for many people sweets become addictive and for that reason should be mostly avoided.

    1. Old wives are much smarter than society tends to give them credit for. (It turns out my Grandmother and Grandma In Law were ,in their own ways, the sharpest people I ever met.) If some people aren’t “born” with a sweet tooth, why would it become addictive for anyone? Why is breastmilk sweet? Nah, we are programmed to like sweet stuff — some just like it/are more prone to addiction than others.

      1. I agree. I know a pair of siblings who grew up in a devastated country in the aftermath of WWII. They both received a lot of sweets and chocolates from GIs. One ate all her candy, the other wasn’t interested in the sweets and stashed them away in a drawer and forgot about them. I think the sweet-toothed sibling ate those too!

  9. Rhiannon, I’m with Mark. It sounds like you’re overtraining. Have you tried Mark’s “intuitive” approach to working out? i.e. whenever feel the urge to workout do it and if not, don’t?

    Granted, you don’t get as jacked appearance-wise as when you force extra workouts but you also feel 3 times better…

  10. I would also suggest a fish oil supplement to anyone suffering from sore, stiff muscles. That’s what saved me when I started doing CrossFit. It makes a huge difference.

  11. I often wake up a bit sore after lifting days.

    One thing that really helps me is bodyweight squats, all the way down, in the morning after I’ve been out of bed for a few. The first couple of reps are pretty stiff and slow, but by the end of the set everything’s groovy.

    Another thing that helps is brisk walking for at least 10 minutes at a time. Gets the circulation flowing and everything that was sore starts feeling fantastic.

    What certainly does not help is sitting down!

    1. I find it extremely helpful to do the “cat-cow” back activation first thing every morning. I think I learned this from Sadie Nardini– I highly recommend her YouTube yoga videos.

      1. +1 for cat cow! This is something that was taught to me way back before I started lifting, when I had back problems. It brought me a lot of relief.

        Gonna dust that off and try it out again. Thanks for the reminder and the video tip!

        1. Hope you enjoy Sadie’s vids as much as I do! The specific one I learned that from is called “wake up yoga in bed.” Feels great! 🙂

  12. Best thing in the world for post workout stiffness is Proteolytic Enzymes. These are used a lot in Europe- in Germany the ambulances carry them. The protocol is a big dose (I do 15 or so first thing in the morning on an empty stomach, then wait 30 minutes to an hour before eating. If you want a 2nd dose, wait at least 3 hours after you eat and take ten. Best product I know id by Biotics Research, called Intenzyme. Also great for healing. A very badly sprained knee a few weeks ago was fine in four days on this protocol.

  13. I read somewhere that vitamin C (or foods rich in C) taken along with oxalates helps reduce any ill effects– do youknow if this is correct? I hope so because I love spinach/citrus smoothies.

    1. My research says this is not true, Vitamin C doesn’t help…
      -Take magnesium-citrate instead
      -Brew “chanca piedra tea” AKA “Stone crusher tea” AKA phyllanthus niruri tea instead. Tons of clinical research supporting its efficacy on PubMed.
      -Eat calcium-rich foods with your oxalates like milk/parmesan
      -Old wives also recommend lemon juice and apple cider vinegar

  14. The mention of the obesity year-long fast should be qualified..they were given water & supplements.

    What exactly is the point of a week-long fast?

  15. Strong But Stiff: does the writer stretch out after every workout? I would wager this is the reason s/he is feeling stuff the next day.

  16. Mark is the man. I’m a natural doctor and I read a lot and I still learn more from his damn daily blog every day. Oxalic Acid excretion change based on gut flora? Meaning diet may alter gut flora and that is what contributes to stone formation? Not just diet alone? First I’ve seen of it….

  17. To fix muscle stiffness, cut out all dairy from your diet.
    This includes ghee (its still milk fat), butter, chocolates, cheese, and even yogurt. Does not matter if it is of the finest quality, grass fed, organic. Dairy is dairy.

    No dairy whatsoever. Dairy is beneficial to the body for a few hours, and then after that the damage begins. Acne, skin problems, muscle fatigue, muscle stiffness, bowel problems.

    Giving up dairy is easy once you notice how much of a damage food it really is to the body.

    That, and start your day with a glass of whole leaf, lightly steeped green tea. 1 cup is all it takes to get back on track.

    1. Weird, I thought chocolate could be dairy free (actually I do have dark chocolate that is 100% dairy free, made in a factory that has no milk traces at all – google the UK brand called Plamil – and the one I buy is solely sweetened with xylitol).

      Anyway, what is it in the dairy that causes stiffness ? I am asking because ghee is pure fat, has no casein, no lactose. And I would say that “even yogurt” is actually worse than butter and cheese. Not sure how you sort this dairy list from worst to least bad in terms of effect on muscle stiffness. And I should say that it depends on your sensitivity. I have no issues with dairy, I just avoid milk because of bigger amount of lactose and casein.

  18. Hi i have type 2 diabetes, and i’m obese and i have some mobility issues, i have been on a 5 day juice fast, when i started to eat again for three days i had some minor stomach pains and a lot of gas, is there anyway to not have those problems. Iam considering a water fast for weight loss, so how should i do this fast and not run into low blood glucose levels.

    1. You might be asking the wrong group, considering that a juice fast would would probably have too high a ratio of carbs to other nutrients to be considered a healthy option. Fruit juice is probably not a great thing to be focusing on when you have type-2 diabetes.

      I don’t know about the ramifications of fasting and diabetes, but it seems like it would be better to concentrate on getting blood sugar under control and increasing insulin sensitivity – weight loss may be a natural side effect.

  19. What does someone who is following the Primal Blueprint do if they WANT to exercise every day? For those who like to stay active and don’t really want to limit themselves, is there a middle road?

    1. I can’t not exercise every day — it just feels wrong! Daily moderate-to-intense levels of exercise improve my ability to think creatively and to come up with solutions to work problems, etc.

      If you want to exercise every day, go for it! But listen to your body and make sure you don’t overdo any repetitive movements — running, cycling, etc. Know when to push through tiredness, and when to give in to it and just kick back.

  20. A 2 months ago I did a 3-day fast after putting on a few pounds and was quite fascinated by the experience and was surprised how easy it was, but I see no advantage in going for week if you aren’t seriously overweight and if you are just in it for the challenge.
    As Mark noted, lot’s of stressors start kicking in. Even day 2 was easy but by the third day I was really happy to have that steak for lunch.

  21. Regarding the “problem” of heat denaturing proteins: the harsh acidic environment of the stomach probably does that anyway. A real non-issue here, nicely deflected by Mark’s excellent answer.

  22. Thanks for the Angelo dela Cruz video/link — just what I needed!

  23. My experience with fasting.
    It started about 6 months ago with an attack of pancreatitis. Initially mis-diagnosed and sent home, I had severe abdominal pain for 2 days that prevented me from eating. I felt dizzy from lack of food. Went back to emergency room and was hospitalized. The treatment is to give you pain meds and to fast until the problem goes away. It took 3 more days, so that’s 5 total. Felt pretty good at the end and lost 8 lbs. Decided to try to keep loosing, and learned a ton about low carb & primal eating & IM fasting. Have lost 60 lbs and have about 25 to go. Often do 16 hr fasts, a couple of 24 hr fasts, a couple of 48 hrs, and one 80 hr fast. I find it realtively easy now. No dizzyness. In fact, the 2nd & 3rd days are easier than the 1st. Been doing the primal fitness routine and tracking progress. The fasts don’t seem to have any ill effects on my growing strength, or energy level. There is a certain feeling of freedom from knowing you don’t have to eat 3 meals a day every day, and that you can not only survive several days on just water but feel good in the process.

  24. dead right.I fasted for six weeks once.drank tea or water.lost 7 stone and felt wonderful

  25. Very timely post about oxalates. The more I read on the internet, the more scared I am to eat certain foods. No nightshades, oxalates, salicylates, fodmaps, etc.. The list of foods that I “should” eat is getting smaller and smaller. It makes my head spin.

    1. If you have the right gut bacteria (oxalobacter formigenes) to process oxalates you shouldn’t worry about oxalates. You can get your gut-bacteria analyzed by mail, I used Ubiome in San Francisco for free through my insurance.

  26. My personal experience with fasting (H2O only) is that it is extremely helpful wih RA. Over the past few years I have done a few fasts lasting 7-10 days. I rest and do not work during the fast. I sleep as much as I need to whenver I need to and take a leisurely walk outside everyday. Consistently after the third day, I have NO pain and signs of inflammation are almost completely gone from my body. I feel good even if my energy is lower than normal. I feel great when I come off the fast. Now I’m just working on finding all offending foods, sleeping enough, and handling stress in a positive manner with the help of MDA, of course.

  27. I have heard that regular (daily) consumption of kombucha (say 4oz p/day) will prevent kidney stones or dissolve existing stones. I think this is because of the acidic properties of kombucha.

  28. I will be going on a winter solstice fast tomorrow December 21st. I will eat dinner tonight and nothing the next day. I will eat again the next morning or that night depending on how I feel.

  29. I’m stiff and sore every single day it seems. Everything makes me stiff and sore. Everything. I had hoped getting stronger would stop this, but it isn’t working. I don’t think anything is going to work. I think I will always be fat and sore.

  30. A week long fast is extreme. I’ve done about a 46 hour fast and it left me feeling quite famished.

  31. Week long fasts. I follow the research on the subject and have never seen anything positive in the papers I have seen to suggest a week long fast is in any way helpful. I do see the spiritual argument but don’t happen to buy into it. Beware the temptation to assume more is better.
    I undertook three 72-hour water fasts in the first six months of this year, with specific health (auto immune) results in mind. And there’s some science behind it – at least one study. And I am a regular faster of 24 hours once per week (last 4 years) and use protein saving fasts for the first half of most days (Whey and Kefir with potato starch, so not really a fast). The 72 hours is suprisingly easy so long as I’m not around food. If I have to prepare food for my family, I can be in trouble. Some auto immune issues did respond to the 72 hour fast but falling returns meant that I seemed to get much less from the third than I did from the first.

  32. I appreciate you Mark (and team). I just spent 3 days (16+ hours) doing research on oxalates for my calcium-oxalate kidney stones, reading dozens of clinical trials and science on the matter and foolishly waited too long to check the Daily Apple… all I would add is that it appears we (oxalate kidney stone formers) lack the bacteria oxalobacter formigenes which breaks down oxalates in the large intestine before absorption into the kidneys. I confirmed this by having my gut bacteria analyzed by Ubiome in San Francisco.

    There is no supplement or known food source for the colonization of oxalobacter formigenes in the large intestine. There is a company OxThera working on it but they are in clinical trials. Contacted OpenBiome (the poo-pill guys) and they don’t select for specific strains and only supply for those who suffer C.diff anyway.

    I’ve resolved to limiting my oxalate intake and when I do have some oxalates will be pairing them with calcium-rich foods (milk/parmesan) and magnesium citrate. Also found a great amazonian tea I’m brewing daily known as Chanca Piedra (Stone-crusher in Spanish) whose scientific name is phyllanthus niruri and you can find dozens of clinical trial vouching for its efficacy against calcium-oxalate kidney stone formation on PubMed. Further, I’m adding fresh lemon to my tea and apple cider vinegar to me Zevia brand sodas which I dilute at a 1:4 ratio in sodium-free sparkling water. I read these help according to old wive’s tales.

    When the stones come, I forget the water, opiates, and NSAIDs…
    I find lots of wine and weed get me through it LIKE A BOSS!!!!!

    PS: If you have the bacteria oxalobacter formigenes and don’t form kidney stones I wouldn’t worry about oxalates, your guy is made to process them and a low oxalate diet is far more damagingly low in dietary magnesium 🙁