Can Intermittent Fasting Slow Hair Growth? Study Sheds Light

Intermittent fasting has proven benefits for metabolic health, but a new study shows that it could slow hair growt-at least in mice. Researchers report in the Cell Press journal Cell that mice subjected to intermittent fasting regimes showed improved metabolic health but slower hair regeneration compared to mice with 24/7 access to food. A similar process might occur in humans, based on a small clinical trial that the team also conducted, but it’s likely to be less severe since humans have a much slower metabolic rate and different hair growth patterns compared to mice.

The researchers examined hair regrowth in mice that were shaved and then subjected to different intermittent fasting regimes. Some mice were fed on a time-restricted feeding (TRF) schedule that involved 8 hours of food access and 16 hours of fasting each day, while other mice were subjected to alternate-day feeding.

They were surprised to find that fasting inhibited hair regeneration. While control mice that had unlimited access to food had regrown most of their hair after 30 days, mice on both intermittent fasting regimes showed only partial hair regrowth after 96 days.

The team showed that this inhibited hair growth occurs because hair follicle stem cells (HFSCs) are unable to cope with the oxidative stress associated with switching from using glucose to fat. Using genetic engineering methods, the team showed that the fasting-induced apoptosis was driven by an increased concentration of free fatty acids near the hair follicles, which caused a build-up of harmful radical oxygen species within the hair follicle stem cells. Free fatty acids also caused human hair follicle stem cells to undergo apoptosis in vitro.

In comparison, epidermal stem cells, which are responsible for maintaining the epidermal skin barrier, were unaffected by intermittent fasting. The major difference between these stem cell types is that epidermal stem cells have a higher antioxidant capacity. When the team tested whether antioxidants could mitigate the effects of fasting on hair growth, they showed that both topical application of vitamin E and genetic upregulation of antioxidant capacity helped hair follicle stem cells survive fasting.

The team also conducted a small clinical trial with 49 healthy young adults to examine whether fasting similarly affects hair regrowth in humans. They showed that a time-restricted diet involving 18 hours of fasting per day reduced the average speed of hair growth by 18% compared to controls, but larger studies would be needed to verify this effect given the study’s small sample size and short duration.

Reference: Intermittent fasting triggers interorgan communication to suppress hair follicle regeneration, Chen, Han et al.Cell, Volume 0, Issue 0