What Intermittent Fasting Really Does To Your Hair (Hint: It Doesn’t Make It Grow) – Health Digest

Intermittent fasting (sometimes called time-restricted eating) may help to keep you from overeating without forcing you to count every calorie. However, intermittent fasting has cons that might leave your tresses in a figurative tangle. In fact, if you’re not paying attention to the foods you consume during your eating window, you may end up with less-than-nourished hair.

To find out why and how intermittent fasting can affect hair, Health Digest asked Jana Greene Hand, a Registered Dietitian, for assistance. Hand explained that although intermittent fasting can be right for some people, it isn’t without its downsides. “While there are plenty of benefits to intermittent fasting, such as weight loss and reduction of inflammation in the body, there can be unpleasant side effects as well, such as the thinning of hair.” 

Hand added that due to the inherent calorie restrictions of intermittent fasting, practitioners can wind up with nutrient deficiencies, and that’s a problem when it comes to hair. “In order to grow thick beautiful hair, the body needs ample protein, iron, zinc and B vitamins,” explained Hand. “Intermittent fasting has been linked to deficiencies of these vital nutrients.”

Intermittent fasting doesn’t just put you at risk of slowing your hair growth due to nutritional deficiencies, either. It may also cause your body’s hormones to react unexpectedly to the stressors of a highly regulated, restrictive eating schedule. According to a 2021 study in Endocrinology and Metabolism, intermittent fasting can have unintentional consequences on the functions of hormones. These hormonal disruptions can interfere with both the look and length of healthy hair.

For instance, Hand noted that intermittent fasting increases cortisol, a stress hormone. The result is that cortisol puts the body into chronic oxidative stress, which she advised could negatively impact hair growth. A 2025 study from Cell concurs with Hand’s observations. The study found that intermittent fasting caused oxidative damage that negatively affected hair follicles, leading to an interruption in hair production.

There’s another hormone-related factor that might create a problem if you’re aiming for lustrous, long locks: a too-slow thyroid. Said Hand, “Intermittent fasting has also been linked to the inhibition of thyroid function which slows down hair follicle activity and can lead to dry, brittle hair and hair loss.” (Hair loss is one of the symptoms of thyroid disorder you shouldn’t ignore.)

Still interested in intermittent fasting but want to bypass all those preventable bad hair days? You can help protect your hair by remembering three tips from Hand.

First, get enough protein. As a 2021 article from the International Journal of Trichology explains, protein is essential for hair growth because hair is made up of protein. Hand’s top recommendations for protein-rich foods to eat during your feeding window are eggs, tofu, chicken, fish, and lean beef.

Secondly, consume plenty of foods that are rich in iron and zinc, including nuts, seeds, and beans. Like protein, iron and zinc are necessary for strong, lengthy hair. A 2018 study from the Indian Journal of Dermatology found that women who were experiencing female-pattern baldness had low levels of both nutrients. In addition to iron and zinc, Hand suggests consuming food sources that contain healthy fats such as olive oil, avocado, and fatty fish.

Hand’s third piece of advice to avoid hair thinning is to practice a more moderate form of intermittent fasting that allows you to eat for longer periods. “To maximize your hair growth, consider shortening your fasting window from 16 hours to something less extreme, like 12-14 hours,” she said.