When it comes to the benefits of fasting there are a lot of studies on overweight individuals and people with chronic illnesses, but there aren’t actually all that many on strength athletes. This is one you should pay attention to.
Intermittent Fasting and Strength Sports
The study, which was published in the Journal of Translational Medicine in 2016, took a hard look at time-restricted feeding, another term for what’s better known as “intermittent fasting” or IF.(1) It’s what it sounds like — sometimes you don’t eat for a while — and probably the most popular version of the protocol is called 16/8. That’s a sixteen-hour fast (half of which you’re typically sleeping) followed by an eight-hour window during which you eat all the calories you’ve planned for that day.
Indisputably, Swedish strength coach Martin Berkhan of Leangains.com is the man responsible for the popularity of 16/8. And again, while some studies have taken a look at this kind of eating, this was the study that looked at the way it’s typically practiced in the strength sports community: combined with a high-protein diet and implemented by men in their late 20s/early 30s who have been lifting heavy weights for at least 5 years.
Thirty-four guys took part in the study and were split into fasting and non-fasting groups. Before and after an eight-week period their basal metabolism, maximal strength, body composition, inflammation, and cardiovascular risk factors were all measured. The results?
If you want to take a negative slant, you can point to the fact that there was no real difference in strength and the fasting group had a larger decrease in testosterone and IGF-1 and an increase in the stress hormone cortisol. But that’s all stuff that happens when you’re in a calorie deficit and since that group also lost more fat, that’s probably the cause — the fasters also had lower triglycerides, more insulin, and less blood sugar.
If you want to make the argument for fasting? Again, they had less body fat (they lost about 3.5 pounds of it versus practically none in the other group), they had blood sugar and triglycerides, plus they had more of the hormone adiponectin, which is involved in energy expenditure and fatty acid breakdown. This authors suggest that this may have played a part in the drop in body fat as well.
[Thinking of trying this out? Here are 3 practical fasting tips for powerlifters.]
Strength coach Greg Nuckols of Stronger By Science writes in his excellent breakdown of this study:
That may be true, and if it is, that would be a real physiological advantage to IF. But I still think the difference in calorie intake is the more likely explanation, especially since there was no preliminary period to ensure all of the subjects were in neutral energy balance before the start of the intervention.
[Read more: 4 benefits of fasting for strength athletes.]
Health Benefits of Intermittent Fasting
While there wasn’t really much else to talk about here, other studies have also linked intermittent fasting to a temporary surge in growth hormone, higher levels of BDNF — think of it as the brain’s growth hormone, it prompts the formation of new brain cells — and increased autophagy, a process during which the body breaks down its own dead and diseased cells.(2)(3) There’s also the simple fact that if you’ve decided you’re not eating for a period of time, it can be a lot easier to stick to a weight loss protocol. (It’s a little tougher to do while bulking, but it can be done.)
Those results weren’t found (or measured) by this study, but it was a significant moment in the movement and it certainly helped to dispel some myths surrounding the feeding protocol, like skipping meals will result in catabolism and “starvation mode.”
References
1. Moro T, et al. Effects of eight weeks of time-restricted feeding (16/8) on basal metabolism, maximal strength, body composition, inflammation, and cardiovascular risk factors in resistance-trained males. J Transl Med. 2016 Oct 13;14(1):290.
2. Cheng CW, et al. Prolonged fasting reduces IGF-1/PKA to promote hematopoietic-stem-cell-based regeneration and reverse immunosuppression. Cell Stem Cell. 2014 Jun 5;14(6):810-23.
3. Mattson MP, et al. Beneficial effects of intermittent fasting and caloric restriction on the cardiovascular and cerebrovascular systems. J Nutr Biochem. 2005 Mar;16(3):129-37.