Study Suggests Fasting Is Good for Weight Loss, Bad for Hair Loss

You shouldn’t have to choose between losing weight and losing hair — but if you’ve embraced intermittent fasting, that might be precisely the situation you’re in. That, at least, is the conclusion of a paper published this week in the journal Cell. And while the scientists researching this did plenty of work with mice to explore this phenomenon, a clinical trial shows that it also applies to humans.

The researchers behind the paper discovered that, as they phrased it, “intermittent fasting regimens inhibit hair follicle regeneration by selectively inducing apoptosis in activated hair follicle stem cells.”

In these experiments, the scientists sought to gain a better understanding of how fasting affected skin. As they pointed out, hair follicle stem cells help us grow more hair; with a loss of those stem cells comes, essentially, hair loss. To study the effects of fasting on hair follicle stem cells, they initially shaved a group of mice and tested out two methods of fasting: one time-based and one on alternate days. Both groups of mice, they found, had “significantly impaired hair follicle regeneration.”

Additional testing of the same principle in humans yielded similar results, with humans who were fasting showing less hair growth than the control group. When hair did grow back, it was also not the same as before; the study’s authors observed that “many regrown hairs became shorter and thinner in diameter.”

Study Suggests Fasting’s Benefits Might Emerge When It Stops

Is breaking the fast what’s good for you?

MIT biologist Ömer Yilmaz described himself as “shocked” to hear about the study’s conclusions. “We’ve come to expect that fasting is going to be beneficial for most, if not all cell types and good for stem cells,” he told Nature — and noted that these findings showed otherwise. For now, this paper opens the door to further research, and might give some people weighing the benefits of fasting with another variable to consider.