Why Am I Losing Hair on a Keto Diet?

How Common is Hair Loss for People on Keto?

The first thing to know is, hair loss is relatively common in people on ketogenic diets. It doesn’t happen to everyone, but it happens to enough people that it’s a well-recognized phenomenon.

The formal name for the type of hair loss that occurs on keto is telogen effluvium ( 1), and this distinguishes it from other types of hair loss, such as male-pattern baldness, alopecia areata, or hair loss induced by chemotherapy or radiation.

Thinner hair seems like a small price to pay for the wide range of health improvements you experience on a ketogenic diet, but in our image-oriented modern society, losing a lot of hair can have a powerful negative impact on self-esteem and self-image.

As noted in a paper from the American Academy of Family Physicians, “Physicians should be careful not to underestimate the emotional impact of hair loss for some patients.” (2)

Researchers acknowledge hair loss can be a source of anxiety “and distress more profound than its objective severity would appear to justify. This reflects the profound symbolic and psychosocial importance of hair.” ( 3) Women may be more profoundly affected by hair loss than men are—and they’re more likely to notice it if they have longer hair—but men aren’t immune to this.

The Hair Cycle

It’s nearly impossible to notice on a daily basis, but just like other tissues in the body, hair goes through a cycle of renewal, growth, and death. The cycle in each hair follicle includes a growth phase (called anagen), a regression phase (catagen) and a phase of rest (telogen). According to an article in the Journal of Cell Science, “During anagen, follicles produce an entire hair shaft from tip to root; during catagen and telogen, follicles reset and prepare their stem cells so that they can receive the signal to start the next growth phase and make the new hair shaft.” (4) (Click here for a detailed infographic on the hair cycle.)

An average normal scalp has 100,000 hairs, with approximately 86% in anagen, 1% in catagen, and 13% in telogen. ( 5) In telogen effluvium, this ratio shifts dramatically: 70% in anagen and 30% telogen, with as many as 300 hairs shed daily.

We lose old, damaged hair and grow new hair all the time; we usually just don’t notice hair loss unless it’s rapid and/or extreme, as some people experience after being keto for a while.

Telogen Effluvium: Stress-Induced Hair Loss

Telogen effluvium involves abrupt, rapid, generalized shedding of hair and can be thought of as stress-induced hair loss. ( 6) (Generalized means that it’s all over the head, rather than localized to one area or in specific patches.) There are many causes for hair loss, including:

• high fever
• major surgery
• anticoagulant drugs
• giving birth (technically called postpartum alopecia or telogen gravidarum)
• psychological stress
• rapid weight loss

With regard to that last factor, one article used the phrase “crash diets.” ( 7) A ketogenic diet certainly isn’t a crash diet, but physiologically and metabolically, it does mimic some of the effects seen in fasting ( 8) and causes rapid weight loss for many people, so it’s not unreasonable that hair loss could be a result of keto, at least in the short term.

Whether induced by a ketogenic diet or any other type of diet, we don’t typically think of weight loss as “stressful.” (Quite the contrary, for most people: if you started a keto diet to lose weight, when it happens, you don’t feel stressed out; you feel like celebrating!)

However, internally, at the cellular level, the body may perceive the change as a stressor. After all, if you’ve been eating lots of sugar and starch for most of your life and then quit cold turkey, it’s a bit of a shock to your system. There’s bound to be some hiccups, even if most of the changes you experience are positive.

Hair Loss on Calorie Restricted Diets

Even though there are differences between ketogenic diets and very low calorie diets (especially when a very low calorie intake is combined with a large volume of exercise), looking at hair loss in the latter situation can help shed light on the former: According to one paper, nine patients experienced profound hair loss a few months after beginning a vigorous weight loss program during which they lost 11.7 – 24.75 kg (25.8 – 54.5 pounds). ( 9)

Three subjects had experienced similar hair loss multiple times in the past, also after significant weight loss. Researchers speculated that in these cases, telogen effluvium was caused by the severe caloric restriction, with inadequate energy supply to the hair matrix. (This makes sense when you think about it: if the body perceives it’s in an energy crisis, growing long, strong, lustrous hair isn’t its top priority.) Subjects’ hair grew back within several months.

Other case reports in the scientific literature also point to extreme caloric restriction as a cause of telogen effluvium. (10) Again, ketogenic diets are not starvation diets, but they induce similar metabolic changes, in particular rapid fat loss.

Are You Experiencing Hair Loss On Keto?

If you’re experiencing hair loss on keto, it probably didn’t start right away. You probably noticed it several weeks, or more likely a few months, into your new way of eating.

The same occurs with hair loss after giving birth—it doesn’t happen until a few months after. Telogen effluvium involves loss of as much as 30-50% of hair about three months after the precipitating event—such as initiation of a ketogenic diet. (2)

How to Tell if You Have Telogen Effluvium

An alarming amount of hair coming out in the shower or piling up in your hairbrush is the easiest way to gauge if you’re losing more hair than usual after being keto for a little while. Some researchers even referred to it as “clumps of hair” coming out, which you might be able to attest to if you’re experiencing this phenomenon. (11)

You can also do a “hair pull test”: hold about 40–60 hairs between your thumb and forefinger and slide your fingers along the length of the hair while applying steady traction, slightly stretching your scalp as you do. Only a few hairs should come out—less than 10%. More than that is considered evidence of something pathological. (2) Pathological, however, is a loaded term, because the telogen effluvium associated with ketogenic diets is not a disease, and it’s only temporary. Once the body adjusts, the hair grows back.

The Experts Weigh in About Hair Loss on Keto: Be Patient!

Physicians and researchers who work closely with ketogenic diets agree that the hair loss some people experience on keto is only temporary, and nothing to worry about.

According to renowned ketogenic diet researcher Stephen Phinney, MD, PhD, “This hair loss typically occurs 2-4 months after the stress and is temporary, as new hairs start to regrow 2-3 months later.” Sarah Hallberg, DO, concurred in this video clip, and encouraged patients to… well… be patient, and trust that the hair will grow back in time. Eric Westman, MD, discussed the issue of hair loss on keto and reassured viewers that hair loss induced by weight loss is best treated by “tincture of time”—simply giving the body time to adjust and for new, healthier hair to replace what was lost.

Look for Growth of New Hair

Dr. Westman even suggested using a magnifying glass to look for growth of new hair—very short hairs coming in that are hidden by longer hairs and are not noticeable when you’re a few feet away from the mirror. These short hairs are a sign that your hair is growing back just as it should be. Be patient and give those new, healthy hairs time to grow.

Supplements that Can Support Hair Growth

Dr. Hallberg and Dr. Westman also addressed the issue of nutritional supplementation. If someone is truly deficient in something that might support hair growth, such as biotin, iron, zinc, folate, or vitamins A and D ( 30,  31) supplementation might be warranted, however telogen effluvium is not caused by micronutrient deficiencies, so supplementation is unlikely to help.

Other Causes of Hair Loss

Rapid weight loss isn’t the only thing that can cause hair loss. If you’re experiencing hair loss and you’re not new to keto, or you haven’t been losing weight recently, consider some of these other possible contributors to hair loss.

Thyroid Problems

Hair loss is a common sign of abnormal thyroid function, either hypothyroidism or hyperthyroidism. (12) Hypothyroidism (low thyroid hormone levels) is much more common than hyperthyroidism (high levels), and hair loss is a hallmark sign of this ( 13,  14,  15,  16,  17). There have been anecdotal reports of ketogenic diets improving hypothyroidism, but not everyone with low thyroid function experiences this.

Some people see a decrease in their T3 levels (triiodothyronine, the most bioactive form of thyroid hormone) after some length of time on a ketogenic diet. On the surface, this would be interpreted as keto being bad for thyroid function. However, research seems to suggest the opposite: it’s possible keto reduces T3 because the body becomes more metabolically efficient or more sensitive to T3 and needs less of it in order to achieve the same effects.

If someone’s T3 has decreased but they have no signs or symptoms of hypothyroidism, then they do not have hypothyroidism. So far, there is no evidence that well-formulated ketogenic diets that provide adequate calories and micronutrients have a negative impact on thyroid function. (18)

Pharmaceutical Drugs

Various pharmaceutical drugs have been known to cause hair loss, including psychotropic medications ( 19), antidepressants, anti-anxiety drugs ( 20), and mood stabilizers such as lithium, valproate, and carbamazepine. ( 21) Other drugs that can induce hair loss are anticonvulsants (anti-seizure medications), anticoagulants (blood thinners), and beta blockers and ACE inhibitors, both of which are used for high blood pressure. (2)

Autoimmune conditions may also cause hair loss ( 22), and some research indicates that alopecia areata, itself, is an autoimmune condition involving antibodies to the hair follicles. ( 23)

Deficiencies in various nutrients may play a role in hair loss. Research is mixed, but iron deficiency is a potential contributor ( 24,  25) as is a low serum level of zinc. ( 26,  27,  28)

Hair loss is a common phenomenon in people on a keto diet. Here's why it happens, what to expect and what to do about it.