What is fasting?
Fasting is not about eating +3 meals a day thing, very few people do it nowadays. Given what fast food actually is, it’s not surprising actually:
- it’s easily accessible
- it’s quick and simple to consume
- even when full, it causes cravings for more
I typically eat 2 meals a day which means not eating for about 12 – 16hrs a day. This is pattern is known as intermittent-fasting (IF). I first tried IF around 2013 and went on to longer fasts since. I did this by stopping snacking.
Gradually I got used to eating only 2 meals a day and started interspersing 24hr fasts every few weeks. Every few months I’d then turn a whole day of fasting into 2 or 3 days. My longest eventually extended to 5 days.
Why I play around with fasting?
- it’s an easy and cheap experiment to perform
- its myriad of potential health benefits  are too intriguing to ignore
I observed many things from my fasting experiments, but the 2 that surprised me most are the following:
I underestimated how much mental real estate is devoted to food
The mental preoccupation with eating is way stronger than any physical feelings of hunger, which are actually quite mild to non-existent. I didn’t appreciate just how much of our day forms according to our food habits.
You don’t become a skinny weak geek
After 5 days of fasting I could dead-lift +90% of the maximal weight I usually did. I seemed to lose very little lean mass and my weight dropped no more than ~ 2 kgs.
After a week of eating my normal 2 – 3 meals a day, my weight, strength and general exercise performance were right back to baseline. The only (predictable) negatives were a little drop in libido and being a bit less resistant to colder temperatures from day 3 onwards.
It’s amazing how quickly physiology adapts to a lack of food!
All that being said, a ‘fasting diet’ is an extreme practice in the eyes of many. For some of them it is a bigger deal. For instance, diabetics taking insulin or people with hypertension taking blood pressure medication should ask their docs to adjust their meds before experimenting with IF or longer fasts. Others simply should not fast.
Pregnant mothers and young children are an obvious example. Maybe anorexics shouldn’t either. Otherwise, a fasting diet is a simple and safe practice open to virtually everyone. At this point people often think that fasting and starvation are synonymous because you’re not eating in either case.
The critical distinction is that starvation is involuntary and by definition pathological. Fasting is voluntary and perfectly in line with human biology. It’s a perfectly acceptable way for people to (not) eat.
Is fasting good for you?
Depends which animal wants to know. Is a cow well adapted to regular 16hr fasts, say? No. A cow needs to nearly continuously graze in order to fill up its large fermentation chambers  (tummies) that turns grass into amino acids (protein), fatty acids (fats) and some simple carbohydrates (sugars). This takes quite a bit of time. But we care about humans, so are we humans well adapted to regular 16hr fasts? Yes – or at least we should be.
The foods humans tend to have evolved on  are much more calorically and micronutrient dense  than grasses. To make the most of these foods, humans have a very different gastrointestinal (tummy) anatomy , notably a much lower capacity to ferment fibers. Instead we have a much larger small intestine – confusing, I know – that allows us to quickly absorb dense foods like fatty fish or honey.
So first, we can get a lot of calories quickly thanks to the kind of foods we eat and our ability to absorb them efficiently. Second, we can store a lot of these calories to use them when there’s no food around. Impressively, the average lean adult male can store tens of thousands of calories as fat! Third, we can turn this stored fat into ketones  (see more: Ketogenic diet 101: Make Fat Work For You) .
Generating lots of ketones from fat is essential to our ability to fast . When fasting, ketones help maintain our lean body mass . Ketones also fuel many different tissues efficiently, thereby sparing precious glucose for parts of our brain, immune system and red blood cells that cannot do without.
But what about advice from dietitians and nutritionists saying you should not go more than a few hours without eating? It’s wrong. In fact it’s downright harmful ! The 1970s are calling, they’d like their pseudoscience back please.
The power of fasting…
There’s much more to say about fasting. Evidence is being gathered about it being a tool in cancer prevention and in cancer treatment , specifically by making chemo more effective whilst decrease the horrible side-effects .
With all the caveats mentioned above regarding who should consult their doc first or not fast at all, I’d suggest you try the following self-experiment:
- If you’re snacking daily (and you probably are) trying cutting that out first
- Then try 2 meals a day for a week
See where that leaves you.
There’s way more to explore about fasting but today should be a good start. Next time we’ll look at fasting affects our immune system.