Benefits of Alternate Day Fasting

A friend of mine named Dave saw the BBC program Eat, Fast and Live Longer ten months ago. The program promotes intermittent fasting for better health. It sounded good. Already he often went a day without food. Some Brahmins in South India had eaten this way for millennia – which suggested it made some sense. It wasn’t a fad. Alternate day fasting was simpler than the “fast 2 days per week” regimen the TV show ended with. He started alternate day fasting immediately.

It was easy to start. The first day was hard. He had painful stomach cramps, but hunger was not a problem. The second day of fasting was slightly difficult, again because of stomach cramps. By the third day of fasting, there was no problem. He tried eating a small meal (400-500 calories) on fasting days but it just made him hungry. It was easier to not eat at all.

Within two weeks, his head felt clearer, he had more energy, and he felt lighter. Lots of people say the same thing in YouTube videos about the diet. He had more mental energy. Before the diet, he easily became overwhelmed. In spite of a highly technical background (he was a math professor at an Ivy League school), something as simple as writing a computer program would exhaust him. When he tried to tackle a technical problem, he would get overwhelmed, exhausted, and would quickly give up. For example, he has written tens of thousands of lines of computer code. Writing in a language he knew very well, he’d be unable to get beyond 10-15 lines. Within three months of starting the diet, he took an online class (an introductory class about R) and was surprised he could do the work. (He had started the class to take his mind off of family issues he had to deal with. He wanted to do something for himself.) After that, he took two more online classes, about cryptography and about functional programming. He finished them and did well. He was elated.

Several other things started improving. He’d had GERD (“acid reflux”). He had poor digestion at night, would wake up with an “acidic stomach” and burning in the back of his throat and mouth. He’d had this all his life (he’s now in his fifties). In his twenties, several health experts told him he had digestive problems. When he started alternate day fasting, he didn’t change the time of day that he ate. After two or three months, his GERD entirely went away.

Another improvement was athlete’s foot. He’d had it since his mid-twenties. He had it all over his feet, not just the toes. He’d done many things to get rid of it. None of them worked, at least permanently. After two months of alternate day fasting, he noticed improvement. Over the following months his athlete’s foot continued to improve. However, three weeks ago he started drinking a half-gallon of yogurt per week. Within two weeks of starting that, his athlete’s foot got much worse. Eating much more yogurt was the only dietary change he’d made. The connection (yogurt increased athlete’s foot) is plausible because athlete’s foot is due to one or more fungi, fungi need sulfur to grow, and yogurt contains a lot of cysteine, which contains sulfur. (A natural therapy site gets it exactly wrong: “Continuing to consume yogurt . . . on a daily basis after the immediate problem has been solved may prevent future outbreaks”).

His food allergies started going away. Wheat was the worst. After eating wheat, he got brain fog, agitation (difficulty sitting still), and difficulty focusing. He would start having violent imagery; for example, his dreams will get quite violent. A laboratory test showed that he had astronomical levels of an immune response to gluten peptides. Another food allergy of his was dairy. It caused agitation, difficulty concentrating, and depression (in the sense that you feel like you want to kill yourself). Before he figured this out, there were times he consumed a quart of milk in a short period of time. Half an hour later, he got these three symptoms, including scary depression (“there’s no way out”). Now he can consume both wheat and dairy without trouble. His wheat allergy isn’t entirely gone but it is much better. He hasn’t noticed any allergic reaction to dairy, even large amounts.

He’d had blood sugar problems for a long time. He’d had hypoglycemia since his late twenties. After strenuous exercise, he could come close to passing out. He would eat fruit to keep this from happening. He’d be lying on the floor, drag himself to eat a piece of fruit, and instantly feel better. After a meal, he’d feel tired, then eat something sweet and feel a rush of energy. He had a regular need for sweet things, including dessert. Whenever he had dinner, he’d really want dessert. About eight months after he started alternate day fasting, he realized that his craving for something sweet went away. One day it was present, the next day gone. Instead of feeling tired after a big meal, he felt calm.

He thinks that he must have had a candida infection and his gut is healing. This would explain the allergies going away and the GERD improvement. He hadn’t expected these changes. He just started it because it fit his eating patterns and was more regular.

“I’ve experienced hunger for the first time,” he says. If he doesn’t eat the morning of a day he’s supposed to eat, he feels ravenously hungry – a new experience. A crystal-clear sense of hunger, which is pleasant. It’s pleasant to know what hunger is. He takes meals more seriously, because that’s the day he’s eating. He pays more attention to his food.

I found his experience far more convincing than anything else I’d heard about intermittent fasting. It was sustainable, it was easy, the benefits were unexpected, no ideology was involved, all sorts of things got better. It was as if this was the eating pattern our bodies were built for. My friend’s experience led me to try alternate day fasting, as I’ve said. After a few days my fasting blood sugar substantially improved (from the mid-90s to the mid-80s). Within weeks, my HbA1c went from 5.8 to 5.4. I haven’t noticed mental changes but my brain test scores have improved for reasons I cannot yet explain (there are several possible explanations).

17 Replies to “Benefits of Alternate Day Fasting”

  1. Funny. The title of the show reminded me of the book about grammar by Lynne Truss: “Eats, Shoots & Leaves”. I think that the show is “Eat, Fast and Live Longer” and not “Eat Fast and Live Longer”. While reading the first paragraph I was trying to figure out why eating fast could be healthful…

    Thanks for the link. I’ve been fasting about one day a week. Feels good.

    Seth: I thought the title was a joke like that but I checked and you’re right, there is a comma.

  2. Possibly related: a dermatologist told me to use any topical medication morning and evening, then skip a day completely, and continue to alternate. This keeps one from becoming inured to the medication, he said, and results in optimal effectiveness.
    Perhaps we should also work every other day, instead of five days a week and then two days off…

  3. I had had plantar warts for a couple of years prior to starting IF (eating in a four-hour window each night). They cleared up almost immediately.

    Seth: Quite surprising, but in agreement with what happened to my friend, especially the disappearance of his athlete’s foot. The Wikipedia entry for plantar warts says nothing about intermittent fasting.

  4. Thank you, Nancy. I was particularly interested in the suggestion that colonoscopies are a bet against the odds.

  5. His food allergies started going away. Wheat was the worst. After eating wheat, he got brain fog, agitation (difficulty sitting still), and difficulty focusing.

    Why would he keep eating wheat????

    What is wrong with people?

    Seth: After he figured this out, he ate almost no wheat.

  6. Seth, do you suppose that there is any particular benefit to Alternate-Day-Fasting over other IF regimes like the 18:6? Do you know have any intuition for the dynamics of fasting (the longer you fast, the better results? or, is there any optimal time to for a fast? 24 hours? 18? 16?)

    Seth: I suppose the longer you can fast without discomfort, the better. I can do alternate day fasting forever, it is pleasant rather than unpleasant. I used to eat one meal per day plus snacks. Plainly alternate day fasting is better.

  7. @Elizabeth Molin “Perhaps we should also work every other day, instead of five days a week and then two days off…”

    Exactly what I did back in 2011.

    I realised I couldn’t handle spending all week at work, and I’d also built up enough leave to take 2-3 months holiday. Instead of doing that, I asked my boss if I could just come in M-W-F, he agreed, and I tell you what everything just makes sense when you do it like that.

    So yeah, picture this – every day that you go to work, you know you have a day off tomorrow. And when it’s Friday – you get two!

    As for eating, I do what I call Intermittent Feasting.

    Seth: When your “only work MWF” schedule stopped, what happened?

  8. Hi Seth, I’ve followed and have been interested in IF and ADF for a year or so and have had mixed results. Just doing some reading/reviewing of the yahoo link you provided and there are a few posts regarding atrial fibrillation and stiff heart disease. Not sure what to make of them, but in general have heard mostly positive things in relation to the heart and fasting. Have a look:

    Also, mentioning the heart:

  9. Seth –

    What do you eat on your fasting days when you’re consuming 700 – 800 calories?

    Seth: Butter, flaxseed oil, and a few other things.

  10. Seth –

    Thanks for the details. I’ve been eating butter, flaxseed oil and home made kefir from all your posts on the health benefits. Any thoughts on the health pros and cons of eating less of these foods or even skipping them completely some days while doing alternative day fasting?

    Seth: No, I have no relevant experience. I eat butter and flaxseed oil on fast days, for what it’s worth. I want to keep brain function constant so that I can study the effect of other things on brain function.

  11. jclifton – from a cursory reading of the first paper, I wasn’t clear what the diet comprised. I think food composition does make a difference to heart function. I’m yet to be convinced of the alternate day fasting as the cause-effect factor in atrial fibrillation and stiff heart disease. I used to experience heart palpitations when I followed a low carb diet and had protein shakes with lots of whey protein and leucine. When I reduced the protein powders, the heart was fine.

    I’m doing a version of shangri la on one meal a day. I’ve switched from oil to butter (oil fine at first, but in the second week I started to retch) and no heart problems.


  12. Interesting. I assume he drank water. Did he consume any liquid calories or probiotics (Yakult?) on his fasting days? I’m tempted to try this – spare no detail.

    Something is missing in the story. He didn’t get to be an Ivy League math professor by being confused, exhausted, overwhelmed and depressed all the time. Were his indigestion and tiredness increasing in severity before he started the diet?

  13. What did he eat on his non-fasting days? I’m curious, because I’m dealing with a candida infection and this account gives me hope.

    Seth: A later post will answer this in detail, but the short answer is: nothing unusual. He did not change his diet when he switched to alternate day fasting.

  14. My story is quite similar – I feel so much better when fasting, with more mental focus. I am more productive and less depressed. I’m assuming I may have candida overgrowth or something.

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