While intermittent fasting has gained popularity for its potential health benefits, a new study published in Cell indicates it may have unintended effects, including slower hair growth. This dietary approach, followed by about 13% of Americans, involves time-restricted eating patterns, such as fasting for 16 hours a day or alternating fasting days.

Slower Hair Growth Observed in Mice

Researchers began their investigation using a mouse model, shaving the animals and feeding them either unrestricted diets or intermittent fasting patterns. After 90 days, mice subjected to intermittent fasting showed only partial hair regrowth, whereas those in the control group had regrown most of their hair within 30 days.

The study attributes this effect to the oxidative stress caused by the metabolic shift from glucose to fat during fasting. Hair follicle stem cells (HFSCs), essential for hair growth, appear less capable of coping with this stress, impairing their function.

Similar Effects Found in Humans

The findings extended to humans in a clinical trial involving 49 young, healthy adults. Participants following an 18-hour daily fasting regimen experienced an 18% reduction in hair growth speed compared to those on regular diets.

According to Bing Zang, Ph.D., principal investigator at Westlake University in China and senior author of the study, the results in humans were milder than in mice due to differences in metabolic rates. However, Zang cautioned that fasting may still disrupt hair follicle function.

“We don’t want to scare people away from intermittent fasting, as it has many beneficial effects,” Zang explained. “But awareness of its potential impact on hair growth is important. Future research will focus on ways to mitigate these effects, including identifying metabolites that support HFSC survival and promote hair regrowth.”

Expert Insights on Hair Growth and Nutrition

Commenting on the study, Jennifer Cheng, D.O., chief of endocrinology at Hackensack Meridian Jersey Shore University Medical Center, noted the need for further human studies to confirm the findings. Similarly, Hans J. Schmidt, M.D., chief of bariatric surgery at Hackensack University Medical Center, highlighted that hair loss is not uncommon during periods of rapid weight loss, regardless of the method.

Dr. Schmidt explained that hair growth occurs in cycles, with phases of growth, rest, and shedding. Intermittent fasting appears to disrupt this cycle by affecting the transition from the resting to the growth phase, leading to slower hair regrowth. He emphasized the need for further research into the mechanisms and potential dietary modifications to prevent hair loss while maintaining the benefits of fasting.

Supporting Hair Growth Through Balanced Nutrition

For those practicing intermittent fasting, nutrition is key to minimizing potential side effects like slower hair growth. Monique Richard, M.S., RDN, LDN, a registered dietitian nutritionist, emphasized the importance of obtaining essential nutrients such as protein, vitamins (A, C, D, E, and B), minerals (iron, zinc, selenium), and essential fatty acids.

“Foods like spinach, eggs, fatty fish, nuts, seeds, and brightly colored produce are rich in nutrients that support hair growth and overall health,” Richard advised. She cautioned against relying on over-the-counter supplements with excessive nutrient concentrations, recommending nutrient-dense meals instead.

“Achieving optimal health—whether it’s glowing skin, shiny hair, or overall vitality—requires consistent daily effort,” Richard added. “Nourish your body with balanced meals and mindful eating rather than quick fixes.”

Looking Ahead

This study underscores the importance of understanding the potential side effects of popular dietary trends. While intermittent fasting offers numerous health benefits, its impact on hair growth highlights the need for individualized approaches to diet and nutrition. Researchers aim to further explore these effects and develop strategies to protect hair follicle health during fasting.