Is Intermittent Fasting Affecting Your Hair’s Thickness and Growth?

Intermittent fasting has become a widely embraced eating pattern for those looking to shed pounds and boost metabolism. Whether it’s the popular 16:8 method or alternate-day fasting, these approaches revolve around eating within specific timeframes, limiting calorie intake during certain hours or days. Many people swear by these regimens, considering them the ultimate key to managing weight effectively and staying lean over time.

However, despite the many reported advantages, a recent study brings to light a lesser-known concern. Researchers now suggest that intermittent fasting might have an unintended impact on your hair. Specifically, it appears this way of eating could dampen the speed at which your hair grows back after shedding or loss. So, while fasting might help your waistline, could it be affecting your hair's fullness and length in an unexpected way?

In a quest to better understand the effects of fasting on the body beyond weight loss, a team led by a stem cell scientist carried out research focusing on hair follicle regeneration. Their investigation aimed to uncover how intermittent fasting influences tissue repair processes, especially those related to the tiny but mighty hair follicles responsible for hair growth.

The experiment was initially conducted on groups of mice, each subjected to distinct eating patterns. Some were allowed to eat whenever they wanted, others had their meals confined to an 8-hour daily window followed by 16 hours of fasting (mimicking the 16:8 method), and a different group fasted every other day — 24 hours without food, then 24 hours of unrestricted eating. After shaving their fur, researchers monitored the mice's hair regrowth over a period lasting more than three months.

To see if these findings held any relevance for humans, a smaller study was also done involving young adults. Here, the researchers shaved a tiny patch of the scalp and measured the new hair's growth after a few days, aiming to observe any delays or changes linked to fasting. This dual approach tied lab results with real-world human observations to paint a fuller picture of the fasting-hair growth connection.

Results from the mouse studies were quite dramatic. Those that ate without limitations saw their hair grow back fully in about a month. Conversely, mice on intermittent fasting schedules showed significant hair thinning and had remaining bald spots even after 100 days, pointing towards a slowdown in hair follicle activity caused by calorie restriction periods.

In the human group, the results were less severe but still meaningful. Participants practicing the 18:6 fasting method demonstrated an approximate 18% reduction in hair regrowth speed compared to those with regular eating habits. While hair density—the number of hairs per square centimeter—did not drastically differ, the hairs that did grow back tended to be thinner and shorter in fasting individuals.

Scientists explained these differences partly stem from species traits. Mice have much faster metabolic rates, so fasting has a stronger effect on their hair follicle stem cells. In humans, the impact appears milder; although some hair follicle stem cells undergo apoptosis (cell death), many survive, enabling hair to regrow but at a slower pace. This nuance may reassure some fasting enthusiasts who have noticed slower hair growth but not complete hair loss.

Even with its widely known health benefits, intermittent fasting might not always be an ideal choice for everyone, especially those concerned about maintaining strong and healthy hair. The study introduces a concept rooted in biology and evolution — during times of scarce food, our ancestors' bodies naturally slowed down certain processes, such as hair regeneration, to conserve energy for critical organs like the brain.

This ancient survival mechanism may get unintentionally triggered by modern intermittent fasting, leading to slower hair regrowth. It raises a thought-provoking question: Is the trade-off between managing weight and hair vitality worth it for you personally? Knowing this, you might want to reflect on how your body is responding to your diet and what your priorities are when it comes to overall wellness.

Experts emphasize that more extensive research is needed to fully understand these effects, given the initial study involved relatively few human participants. Still, the takeaway is clear: diets and fasting routines don’t impact everyone in the same way, and some downsides could accompany even the healthiest habits.

If you’re actively trying to promote hair growth, it might be beneficial to focus on a well-rounded diet packed with vitamins, proteins, and minerals essential for hair health, and to maintain consistent eating schedules. And if you’re considering intermittent fasting or already practicing it, discussing your plans with a healthcare professional or a dietician can help tailor an approach that supports both your metabolic and hair care goals.