Dear Mark: Fasting Followup

inline_Fasting_follow-upFor today’s edition of Dear Mark, I’m answering questions from the comment section of last week’s fasting post. You guys brought up some great points, and I’ll be addressing some of them. First up, do you need to follow a vegan diet to maintain the health benefits of long fasts? Second, I give a tip or two for appetite suppression during the fast. Then I discuss my definition of a long fast, the potential effect of fasting on gut bacteria (and whether we should consume prebiotics and probiotics while fasting), the reason why fasting makes some people have short fuses, and whether green tea k0mbucha breaks the fast.

Let’s go:

Mark–For the autoimmune case reports, you failed to mention that the patients preceded and followed the fast with a vegan diet, and that the authors conclude the paper by saying a vegan diet appears to be necessary to sustain the results.

Good catch, Margaret. I saw that, knew someone would mention it, and decided to address the inevitable query in a Dear Mark rather than drag it out in the middle of a post.

For one, these are case studies, and case studies notoriously lack the ability to imply causality or make conclusions. They are rigorously-recorded anecdotes containing a seed of a hypothesis for further, more serious study. So even though all the subjects followed a vegan diet, and the authors opine that such diets are necessary for long-term maintenance, we don’t have anything to compare it to. The same applies to the long fast, of course—the case studies can’t establish whether the fasts are actually responsible for the improvements.

Second, my guess is that they’re just assuming the validity of the conventional wisdom. “Of course, vegan diets are the healthiest, least inflammatory diet in the world, so let’s have these recovering fasters follow the healthiest diet in the world.” Is it really necessary?

Your “average” vegan gets more of certain nutrients than your average omnivore, particularly folate, magnesium, vitamins C and E, copper, and fiber. Your average omnivore gets more protein, vitamin D, vitamins B2 and B12, zinc, and iodine than everyone else. Fish eaters eat the most calcium and selenium.

Why not be all three?

There’s certainly strong evidence that healthy omnivorous diets aren’t any worse than plant-based ones for cancer risk, and sometimes they’re better.

Unless the contention is that the recommendations for adequate intake of vitamin D, vitamin B2, vitamin B12, protein, zinc, iodine, calcium, and selenium don’t apply to patients with autoimmune disease….

Lifelong vegetarianism has no effect on breast cancer risk, nor does it affect prostate, colorectal, or (again) breast cancer risk. If anything, “vegetarians” who eat fish have a lower risk of colorectal cancer than strict vegetarians.

For rheumatoid arthritis—the autoimmune disease featured most prominently among the case studies—removing gluten might be the crucial piece of these plant-based diets. A gluten-free vegetarian diet improved symptoms in RA patients, for example, and another gluten-free vegan diet reduced symptoms and improved biomarkers in RA patients. As immunoreactivity to dietary allergens reduced, so did RA symptoms.

Could you get the same results by keeping the gluten out and adding some wild caught salmon and pastured eggs to go with your “vegan” diet? I think so, and I hope we find out for sure some day.

I occasionally do a fast for 24 hours. For an appetite suppressant, I drink ginger tea made from boiling chopped ginger root. Do any of you have suggestions for other appetite suppressants?

Coffee is a good appetite suppressant. The literature is mixed, but caffeine seems to reduce food intake, probably due to increased lipolysis. With more body fat available for burning, you have less desire for food.

Staying active might be the best, though. Not active as in hiking the Appalachian trail or taking CrossFit classes. Active as in busy. Engaged. Walking, working, reading, creating, gardening. Keep mind and body busy, and your thoughts will be less likely to stray toward boredom-induced hunger.

What is considered a long fast. My usual is 36-45ish, that still be considered short?

In my book, a long fast lasts at least three days. But even two days is “long” for most people. Heck, skipping lunch is absolutely bonkers these days.

What’s the impact of extended fasting on gut flora (the microbiome)? Those lifeforms are obviously going to be stressed, perhaps to net benefit, but that would be conjecture.

And if there are hazards there, could they be mitigated by supplementing with probiotics and daily non-caloric prebiotic fiber to keep the critters happy?

Fasts can be good for us. Maybe a fast is good for those tiny guys living in your gut, too. They’ve co-evolved with humans, relying on us for food. We don’t always get food, so they must be adapted to occasional bouts of not getting any either. They may also be adapted to our current practice of perpetual snacking, given that bacterial generations can be as short as 20 minutes and evolution happens rapidly. (Although since bacterial generations can be as short as 15-20 minutes, perhaps they’ve adapted to the grazing.)

Also, many species of gut bacteria feed on mucin produced by the gut lining. This isn’t sustainable in perpetuity, as mucin maintains the integrity of the gut lining, but there’s no problem for a few days. They’re equipped for it. A 2015 study on “fasting”—mostly fasting with some low-calorie soups and juices—found big increases in mucin-degrading bacteria.

I’ve used a three days fast to clear up some pretty bad stomach issues. Whenever my dogs have diarrhea, I fast them for least a whole day and it always clears up. If “lack of diarrhea” indicates good gut health, I’d say fasting has a neutral or beneficial effect—at least if there’s an existing problem.

Hold off on the probiotics and prebiotics until you’re back. It probably wouldn’t hurt, but I’m interested in fasting the bugs, too.

One thing worth considering with longer fasts is the effect (or possible effect) on mood/personality… I saw Rachel Hunter (on her tv series Tour of Beauty) do a week or 2 fast and she admitted that she got very angry/aggressive/ easily annoyed etc… However she wasn’t primal/paleo to begin with so maybe someone who is already a fat-burning-beast wouldn’t have such side effects, and it was a “TV Series” so I’m not sure how much faith we can put in that, but she did seem genuinely irritable (maybe try meditation, yoga etc when doing longer faster for your family’s sake ?

That’s certainly possible, but I find—and the research backs this up—longer fasts imbue me with euphoria. It’s tough to get angry when the mundane suddenly seems profound. The most likely explanation is exactly your instinct: She wasn’t an effective fat burner. Fat-burners hit the ground running. They can tap into their fat stores and avoid the worst of it. Sugar-burners will go through major withdrawals and deal with a terrible case of low-carb flu.

My question is about the use of green tea Kombucha during an extended fast – would this be something you recommend as I have been using it for a while now and love it…?

Sure. As long as the kombucha culture has digested the majority of the sugar, and there’s not enough residual sugar to break your fast, it should be fine.

The green tea component of the kombucha could actually be really helpful. One study found that green tea protects against the fasting-induced damage to the intestinal lining during a 3-day fast. 

Thanks for reading, everyone. Take care!


TAGS:  dear mark

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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22 thoughts on “Dear Mark: Fasting Followup”

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  1. I just finished up my first 38 hour fast this morning at 6 am. I found that I did fine up til about dinner time. At this point I found myself to be hungry. Manageable but hungry. I still made my breakfast for the next 5 days, cooked dinner for my wife and daughter and even sat with them at the table while they ate. I feel like I have more energy after the fast. Is this normal? Also we walked about 2 miles and still did all of our other fun family items during. Is that a bad idea when fasting?

  2. I tend to skip breakfast 2-3 days a week (I work as a personal trainer so lots of output most days) and have never tried a longer fast than that. Things seems to be working great so I do not know if I need to mess with them.

    My wife and I talk about eating lunch on Saturday, having a low-key night and then not eating again until late Sunday afternoon. Seems like a relatively painless way to go 24-hours without food.

  3. When calculating a time period for a fast (especially the shorter 18- or 24-hour fasts), shouldn’t you consider the 6 to 8 hours it takes to digest your last meal? It seems that just because you’ve stopped putting food in your mouth, the clock on your fast shouldn’t immediately start ticking.

    1. Good point. A normal day for me is dinner by 7pm and no food until lunch the next day. However, I don’t consider that a 17-hour fast. In fact I don’t consider encompassing much of a fast at all. Even if I skip lunch and go 24 hours between meals I don’t consider myself in any kind of deprivation scenario for maybe more than a few hours. That obviously has to do with being well-satiated by the previous night’s dinner.

  4. Any tips on controlling the embarrassing stomach grumbling during the first day or so of a fast?

  5. “Clear liquids,” “bowel rest,” “fasting,” whatever. Traditional treatment for bowel issues, pretty darn effective for colitis, diverticulitis, and less serious upsets. More tolerable than the standard regimen of antibiotics, antifungals, and pain killers, without the myriad side effects that just made me more miserable. I refused them at my last ER visit, and was well within a week, well before the prescriptions would have run out. When I have a flare, 3 days of bowel rest works wonders. If it takes longer, so be it.

  6. I recently read “Buddha’s Diet” and tried eating for the 9 hours recommended during
    the daytime and felt great. I also lost weight as long as I stayed on it. I usually didn’t eat after 3 pm or before 7 am. Now I am trying it again but without the oatmeal and grain products. So far, great results. Have you heard about this book ? Basically it is intermittent fasting mentioned in you book.

  7. Even though I’ve never done any type of a real fast, these are fascinating questions. I find ginger tea definitely curbs my appetite. Lately I’ve been steeping fresh ginger in hot water, then adding lemon juice, matcha, and a bit of cayenne pepper. (Actually just posted the “recipe” on my blog.) I just use a teaspoon of matcha to about a half gallon of water, so it’s very diluted. Ginger is definitely the predominant flavor. Sipping this throughout the day is very refreshing and energizing, and I think it curbs my appetite too.

  8. I’m primal and I fast every day from evening meal to evening meal without any problems at all. I’ve done this for the last two years and I always train and exercise in a fasted state.

    The longest I’ve stretched a fast out to is two and a half days and it was completely unplanned. I concur with Mark regarding the euphoria on an extended fast it was incredible.

  9. Fasting does not have to be an all or nothing excercise. I have had a welcome experience with food limitation of no more than three food items for up to one week. Combinations like: wild salmon and black berries, chicken and avocado, eggs and leafy greens, etc. The point is not to starve oneself but condition nutrition intake on a as needed basis. It sure makes shopping easy. Theoretically, Grok did not have the variety of primal options we have today and was limited to what could be hunted and harvested within a several mile hike.

    1. We should not judge Grok’s theoretical existence based on how people live now. We’ve severely limited what we consider to be food, which is a different question from what is edible. Grok did that to a much lesser degree–a lot of traditional groups had food taboos, but the total number of individual species they ate was still far larger than what we willingly eat now.

      In my yard alone there’s enough different plants growing that, spring through early fall, I could almost put together some kind of herbal salad with wild strawberries for dessert. That’s *without* planting a garden.

      On the critter side of the equation, just think Daryl Dixon on steroids. And it wasn’t all guys catching them, either. Small game would have been within the reach of women and older kids.

      1. I’m not judging Grok, but if the river is full of salmon and the banks of that river are covered with ripe blackberries, slugs and nettles become less of a palatable option to me.

  10. For people asking about what to consume during a fast, Dr. Dan Pompa recommends either bone broth or Suero Gold Whey Water. I’ve done a five day bone broth fast myself and it wasn’t easy, even for someone who does intermittent fasting daily. However it was worth it as I felt noticeably better afterwards. I’m considering doing one of these every few months now to give my body a chance to heal and cleanse. More info on broth and whey water here fasts here:

    1. Bone broth contains protein. Consuming protein is not fasting. The whole point of fasting is to restrict protein to promote autophagy, which is where the benefits come from.

  11. When I’m working, I generally eat two meals a day. Either breakfast or lunch, then dinner around 8 or 9 at night. I’ve been out of work since December, and have noticed that I’ve started eating only one meal a few days per week. It’s not planned, I just get busy, then around the 20 or 22 hour mark I realise that I haven’t eaten all day, and am a little hungry. My girlfriend thinks I’m a freak of nature for being able to not only go so long without food, but to do it without being hungry (let alone starving).

  12. Interestingly, they always say that you should feed your dog 3 smaller meals per day (at a set schedule), rather than filling their bowl with a days worth of food, and letting them self regulate. All my dogs growing up have just had a full days worth of food in their bowl, but I thought I’d try the 3 smaller meals thing when I got my dog two years ago. Right from the start, she wouldn’t eat anything in the morning, nibble a little in the afternoon, then chow down in the evening (for some reason, she chows down earlier if my mom or girlfriend comes over). So now I just let her self regulate. Kinda goes to show that intermittent fasting is natural when you’re not living on grains and sugar.

  13. I find reruns of the “Ellen DeGeneres” show to be particularly effective for appetite suppression……seriously

    1. Anyone who tries to use the, uh, *term* “nothingsauce” in a serious debate should be immediately disregarded.