Intermittent Fasting, explained. Dieting, the human lifespan, and rats.
Does intermittent fasting help you lose weight? Increase human lifespan?
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.
“On average, animals that eat 30 percent fewer calories live 30 percent longer. [...] In fact, it is the only method that is universally accepted by scientists to alter the life span of all animals that have been tested so far.”
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 increase a human lifespan — and if it can, which modified variant is best or how many months or years are required to make that kind of difference.
In hopes to improve compliance and research this 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 has 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 a controversial topic within the mainstream industry.
See, there are more than enough diet methods out there 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 length and setup.
Though there’s nothing really exotic about Berkhan’s approach, he was the first to popularize it. Therefore, advocates and critics together responded with… very strong cult-like opinions.
Some argue fasting will 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.
The Study
For 8 weeks, scientists divided young healthy male athletes (5 yrs training experience) into two groups. One time-restricted fasting. The other, nonfasting.
The fasting subjects were instructed to eat only within a 4-hour window on their 4 rest days, and then anything they wanted on days they trained.
The nonfasting group ate anything they wanted at any time.
They self-recorded their food intake at the start of the study and were told to stay within their caloric maintenance.
At the end of the study, researchers found that the fasting group lost ~3.5lb of fat compared to an insignificant loss in the control group.
Except, I think the results provide a weak argumental foundation because dietary recall in studies can be unreliable at best.
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 at the start of the study and then just maintained that slight deficit throughout.
Especially since there was no preliminary period to ensure their subjects were in a neutral energy balance before the start of the intervention.
At the very least, I think this study does lend 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 each session. All while maintaining a high protein diet (1.8-1.9g of protein per kg of bodyweight).
1st session: bench press, incline DB flyes, and curls.
2nd session: military press, leg press, leg extensions, and leg curls.
3rd session: wide grip lat pulldowns, reverse grip lat pulldowns, and triceps press-downs.
All exercises were done for sets of 6-8 reps to failure with 3 minutes of rest between sets.
By the end of the study, the only significant change 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, aside from weight loss, the changes in the fasting group’s blood work did show improved markers for insulin levels, metabolic health, and lower risks of chronic disease.
Like we first saw in the rats earlier.
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 in September of 2017 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:
we are still in the 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, media and public view 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 graze throughout the day and still feel satiated. Though, if you find that approach works for you, then there really 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.
But, it can be a helpful dieting tool.
Just follow a 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.