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Intermittent fasting is an eating pattern in which periods of eating and fasting alternate. Common methods include the 16:8 approach, which involves fasting for 16 hours followed by an 8-hour eating window, and intermittent fasting. About 13 percent of Americans currently practice some form of intermittent fasting, primarily for weight loss and improving metabolism. However, this new study raises questions about their effect on hair growth. A new study published in Cell highlights the potential harms of intermittent fasting, a regimen widely touted for its health benefits. Based on findings from animal and human models, it appears that this approach can significantly slow hair growth. In a new study, Bing Zhang and colleagues from Westlake University in China examined the effects of intermittent fasting on hair regrowth using a mouse model. The mice were subjected to a time-restricted 16:8 diet or an intermittent fasting diet, while the control group had access to food ad libitum. The results were amazing.

Slow hair growth: Fasting mice showed little hair regrowth after 90 days of the experiment, while control mice experienced hair regrowth after about 30 days.

Effects on hair follicle stem cells (HFSCs): HFSCs, which are important for hair regeneration, were unable to withstand the oxidative stress associated with the metabolic switch from glucose to fat during fasting. This led to increased apoptosis (programmed cell death).

This study points to some of the mechanisms that explain how intermittent fasting affects hair growth.

Oxidative stress: When fasting, energy from glucose is converted into fatty acids. HFSCs are not well adapted to the oxidative stress associated with this change. The accumulation of free fatty acids around the hair follicle increases the level of reactive oxygen species, which can damage cells and impair their function.

Hormonal and Metabolic Changes: Intermittent fasting alters the balance of hormone levels and metabolic pathways that are important for maintaining a healthy hair cycle. In particular, it influences the transition of hair follicles from the resting phase to the anagen phase.

Since most of the discoveries were made in mice, some interesting preliminary results from a small clinical trial of 49 people suggest that differences in metabolic rate and hair growth may indicate similar effects, but these are weaker in humans. It was found that people who followed an 18-hour fasting program experienced an 18% decrease in hair growth compared to people who ate a normal diet.

Experts advise caution for those who practice intermittent fasting. According to bariatric surgeon Dr. Hans J. Schmidt, intermittent fasting promotes weight loss, and losing weight too quickly on any diet can lead to hair loss. Likewise, nutritionist Monique Richard emphasizes that nutrition during any diet should be optimized for overall health, which also protects against side effects such as hair loss.