The Science of Intermittent Fasting.
Prefer to watch? Watch our Intermittent Fasting, Explained video.
Despite controversy, fasting itself has been around for thousands of years. Though it wasn’t until 1917, scientists first discovered that reducing the caloric intake in rats would increase the animal’s life span. Fast forward a bit and many studies have further supported this, stating that by fasting every other day, their rats were able to live up to 83% longer.
However — we are not rats. So more studies were initiated to explore the relevance of these life sparing effects in humans.
And following calorie restriction, researchers did find similar results in overweight as well as non-overweight subjects. They’ve also found positive correlations in addition to, or independent of, weight loss. Except, there was one familiar drawback. Human subjects just weren’t able to adhere to their calorie restricted diets.
See, the rats that have seen a positive effect in increasing life spans were either fed low-calorie diets or rotated through periods of fasting for most of their lives. So with the limited research available, still to this day, it’s unclear whether fasting can really increase a human lifespan, and if it can, which modified variant is best or how many weeks, months, years are required to make that kind of difference.
In hopes to improve compliance and research this question further, scientists applied new methods to alternate between periods of average food intake and extended periods of no food intake.
Since then, literature on Intermittent Fasting with alternate diet methods have become more accessible in contemporary media.
Fast forward again to 2006, when Martin Berkhan first publicized his own approach called LeanGains -- and this is when meal timing and meal frequency first started to create something of a controversial topic within the mainstream fitness industry.
See, there are more than enough ways to restrict foods or macros, but Intermittent Fasting skirts all of those details — except for one aspect, the fasting window. And while this concept remains at the center of every fasting diet, the method itself lends to many different variants on the length and setup.
Though there’s nothing really that exotic about Berkhan’s approach, he was the first to popularize it, therefore advocates and critics together have had some... very strong… cult-like opinions in response. Some argued fasting would cause your muscles to immediately atrophy as a result of not eating every 2 hours — while others consider fasting a magical fat-loss hack to “lose fat and gain muscle at the same time.”
See, until 2016, we didn’t have any literature that examined Intermittent Fasting in a set of well-trained athletes. Sadly, this study, while modestly contributing in the right direction, wasn’t at all conclusive. But, I do still think it’s worth exploring.
So here’s the setup: For 8 weeks, scientists divided young healthy male athletes into two groups: one time restricted fasting and the other, non fasting. The fasting subjects were instructed to eat only within a 4-hour window on rest days, and then anything they wanted on the days they trained. Meanwhile, the non fasting group just ate anything they wanted at any time.
They self recorded their food intake at the start of the study and were told to maintain a caloric maintenance by their own account. At the end of the study, researchers found that the fasting group lost around 3.5lb of fat compared to a nonsignificant loss in the control group.
However, I think these results provide a very weak foundation for argument because dietary recall in studies can be… unreliable at best. If anything, one could agree with Berkhan’s conclusions that the scientists likely overstated their results, or simply, that the fasting group was already in a slight deficit and eating a bit below maintenance at the start of the study then just maintained that slight deficit throughout.
Still, at the very least, I think this study does provide some support that meal timing is not a vital component in the risk of muscle loss.
The subjects trained three days per week, varying their exercises within each session -- all while maintaining a high protein diet. By the end of the study, the only significant change observed was their fat mass. Everything relating to strength and lean mass was nearly identical between the two groups. Neither group experienced a change in basal metabolic rate either, but for the most part, aside from weight loss, the changes in the fasting group’s blood work did show improved markers for insulin levels, metabolic health, and lowered risks of chronic disease.
Like we first saw in the rats earlier.
So, this isn’t all that surprising, since we’ve already seen time-restricted fasting methods supported in earlier research. Except, most of the work was on overweight, sedentary people, so it’s fascinating to see similar results in young, well-trained, people.
In fact, an article just published early this September looks extremely promising in favor of Every Other Day fasting as a metabolic treatment for obesity.
That said, I wholeheartedly agree with Dr Bojan’s conclusion that we are still in an infancy stage of research and future exploration with larger sample sizes, longer durations, and better study design is needed before any of this can be validated in humans.
Today, contemporary media and people’s impression of fasting seems to have drifted toward the center.
In the end, I think it’s best to consider Intermittent Fasting as just a dieting strategy, used mainly for, simplicity and adherence. Some find it difficult to eat smaller meals spread throughout the day and still feel satiated. Though, if you find that approach works for you, then there probably isn’t a practical reason to change that. The benefits of meal frequency and timing are going to have, at best, a very small effect compared to your total protein and calorie intake.
What’s important is to simply follow a diet method you can consistently adhere to because if you compensate for the meals you skipped by eating more later in the day, or the next day, or the next, you still won’t lose weight.