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Hair Loss After Weight Loss: Causes, Risks & Prevention

Kristin Hall, FNP

Reviewed by Kristin Hall, FNP

Written by Grace Gallagher

Published 03/16/2021

Updated 09/18/2023

Weight loss can severely improve your health but may have unexpected side effects. Along with having to buy new clothes and field questions from acquaintances about “how you did it,” you might experience physical side effects, like loose skin, feeling cold or even hair loss with weight loss. 

Rest assured, you shouldn’t lose hair after dropping a pants size or two.

Hair loss with weight loss is usually seen in people who shed significant weight or have a nutritional deficiency. The latter means you lack certain vitamins and nutrients, a potential effect of extreme dieting (looking at you, crash diets) or severely restricting calories.

Read on to learn more about the connection between hair loss and weight loss. We’ll also go over what you can do to prevent or treat hair loss from weight loss.

Why Hair Loss From Weight Loss Happens

If you’ve ever experienced rapid hair loss, you know how disorienting it is to see your hair swirling in the shower drain or find clumps in your comb.

Though weight loss is often associated with increased self-esteem, it may have the opposite effect if you lose your hair. Consider hair loss from weight loss a marquee sign for the body: If you’re seeing it, there’s a good chance something’s going on inside.

You probably wouldn’t consider weight loss particularly stressful. Still, it can be a taxing event on the body — the American Academy of Dermatology specifically mentions losing 20 pounds as a stressor that can cause hair loss.

Hair loss from weight loss can happen for a few reasons, and there are several causes of male hair loss.

Male pattern baldness is usually due to a mix of genetic factors and your body’s production of male sex hormones, specifically DHT (dihydrotestosterone), a by-product of testosterone. While every guy produces at least some DHT, some people are more sensitive to its effects than others.

It can also happen because of a nutritional deficiency. And some men experience telogen effluvium, temporary hair loss caused by external factors like illness or certain hairstyles.

If you’ve recently lost a significant amount of weight and are noticing more hair on your pillow, know that hair loss with weight loss is possible. But the good news is it’s usually reversible.

Diet and Hair Loss

If you skip that third slice of pizza or have a salad instead of a burger, your hair probably isn’t going anywhere because of what you’re eating (or not eating, rather). But there is a link between diet and hair loss.

One study looked at 35 patients with female pattern hair loss. Low hemoglobin levels were observed in about 30 percent of participants, and low serum ferritin levels were found in just over 82 percent of cases.

Both hemoglobin and serum ferritin are associated with iron, and iron deficiency is sometimes associated with hair loss. That said, other studies point out that there’s no clear-cut evidence in existing medical literature linking iron deficiency to nonscarring alopecia).

Taking dieting or calorie restriction to extremes? A 2017 study showed that nutritional deficiency could impact hair structure and growth.

The study also showed that having a deficiency in any of the following can cause hair loss:

But why does nutritional deficiency cause hair loss? Thought you’d never ask.

While it may not get your heart rate up or make you short of breath, growing hair actually takes a lot of energy, as hair follicle cells are the most rapidly dividing cells in the body. If you don’t get enough micronutrients from food, your body doesn’t have the fuel it needs to grow hair.

Bariatric Surgery and Hair Loss

Traumatic events and stress (you know, like major surgery) can cause something called telogen effluvium, in which hair gets thrown into a resting state.

You’ve probably heard obesity referred to as an “epidemic,” which sounds dramatic. Still, research shows that if current trends continue, roughly 38 percent of adults will be overweight by 2030, and another 20 percent will be obese.

No numbers need to be crunched to know that’s a whole lot of people. Obesity comes with a slew of health risks, including type 2 diabetes, high blood pressure, cardiovascular disease and stroke.

For some obese people, bariatric surgery (which includes procedures like gastric bypass and sleeve gastrectomy surgeries) is necessary for losing weight and reducing the risk of certain health conditions.

It makes sense that shrinking the stomach to the size of a golf ball would make it tough to get all the nutrients you need. Hair loss after bariatric surgery can sometimes be caused by nutritional deficiencies, including a lack of protein (more on that later).

One systematic review of research found that about 57 percent of people experienced hair loss after bariatric surgery.

We’ll get back to bariatric surgery and hair loss in a second, but first, a quick interruption to recap the hair cycle (we promise this is relevant). The growth cycle of a hair follicle is divided into three stages: anagen (growth), catagen (transition) and telogen (rest).

Temporary hair loss can be caused by stress, illness, hormonal changes or medications. When it comes time for the hair to grow again, usually a few months after the stressful event, all the hairs that were resting will shed at once, causing noticeable (and sometimes alarming) hair loss.

So hair loss from bariatric surgery isn’t just about nutrition — it may also be telogen effluvium.

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Illness and Hair loss

Certain medical conditions and illnesses can cause hair loss in some people.

  • Androgenic alopecia (aka male pattern baldness) affects up to 50 percent of men.

  • Alopecia areata is an autoimmune disease that occurs when the immune system attacks hair follicles in the growth phase, sending them prematurely into the resting phase of the hair growth cycle.

  • Fungal infections of the scalp (sometimes called herpes tonsurans or scalp ringworm) can cause hair loss.

  • Autoimmune disorders that affect the thyroid (like Hashimoto’s and Graves) commonly cause hair loss. This tracks, as thyroid hormones are essential for the health of hair follicles. Antithyroid drugs can also cause hair loss.

  • Anorexia hair loss can be from nutritional deficiencies or extreme weight loss.

  • COVID-19 may cause telogen effluvium.

Protein Deficiency

Hair is primarily made up of protein. So adequate protein intake is essential for hair growth. Low protein intake (or protein deficiency) may lead to hair changes, including hair thinning and hair loss.

Research shows that high-protein diets can deliver 15 to 20 percent greater weight loss than lower-protein diets. Why? They keep you feeling full longer while preserving lean body mass.

Is Weight Loss Hair Loss Dangerous or Permanent?

Now for some good news: Weight loss hair loss is usually not permanent and will stop once you address the underlying cause.

Though excessive weight loss can be dangerous, hair loss itself is not necessarily a health concern.

Telogen effluvium is a type of nonscarring, temporary alopecia triggered by certain life events and changes in your physical or psychological health.

As many as 95 percent of all cases of acute telogen effluvium go into remission. So once your stress levels calm down (one more reason to finally try that yoga class) or you address the nutritional deficiency, you should notice hair regrowth.

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How to Prevent and Treat Hair Loss From Weight Loss

There’s a big difference between hair loss and hair shedding. The American Academy of Dermatology says it’s normal to lose 50 to 100 hairs each day.

If you’re losing more than that or notice diffuse thinning or patches of hair loss, it’s most likely male pattern hair loss. In rare cases, it could be hair loss from weight loss.

Here are proven ways to prevent and slow hair loss from weight loss or other causes:

  • Finasteride (the active ingredient in Propecia®) is proven to slow hair loss and stimulate hair growth. Studies show this medication can reduce the amount of dihydrotestosterone (DHT, a male sex hormone that messes with the hair follicles so they can’t produce new hair) in the body by more than 90 percent.

  • Two’s a party when it comes to our topical finasteride & minoxidil spray. The spray is easy to use and combines two powerful ingredients (finasteride and minoxidil). Finasteride blocks DHT, and minoxidil is a vasodilator, meaning it brings blood to the scalp.

  • Prefer to be in a monogamous relationship with just one hair loss product? Minoxidil is available on its own as minoxidil foam or minoxidil liquid solution.

  • Biotin gummies and biotin supplements are most effective in people with a true deficiency. But if you find out your levels are lower than they should be, they can help.

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Weight Loss and Hair Loss: The Final Word

Here’s the long and short of it (the article, not your hair).

  • Dropping a couple of pounds to fit into the suit you need to wear to a wedding next month isn’t going to make your hair fall out. However, in certain situations like crash diets or illnesses, weight loss can cause hair loss.

  • Hair loss from weight loss is typically temporary and often spurred by a stressful event, such as quickly losing 20 or more pounds.

  • Hair loss treatments can help get your hair back on track.

Check out these tips for making hair grow faster if you’re trying to speed up the growth process after temporary hair loss from weight loss.

Hims offers various hair loss treatments for men — and you can access them online following a consultation with a healthcare provider. Explore your options today.

25 Sources

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  2. Grymowicz, M., Rudnicka E., Podfigurna A., Napierala P., Smolarczyk R., Smolarczyk K., Ewa Rudnicka, Meczekalski B. (2020, Aug.) Hormonal Effects on Hair Follicles. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7432488/
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Editorial Standards

Hims & Hers has strict sourcing guidelines to ensure our content is accurate and current. We rely on peer-reviewed studies, academic research institutions, and medical associations. We strive to use primary sources and refrain from using tertiary references. See a mistake? Let us know at [email protected]!

This article is for informational purposes only and does not constitute medical advice. The information contained herein is not a substitute for and should never be relied upon for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment. Learn more about our editorial standards here.

Kristin Hall, FNP

Kristin Hall is a board-certified Family Nurse Practitioner with decades of experience in clinical practice and leadership. 

She has an extensive background in Family Medicine as both a front-line healthcare provider and clinical leader through her work as a primary care provider, retail health clinician and as Principal Investigator with the NIH

Certified through the American Nurses Credentialing Center, she brings her expertise in Family Medicine into your home by helping people improve their health and actively participate in their own healthcare. 

Kristin is a St. Louis native and earned her master’s degree in Nursing from St. Louis University, and is also a member of the American Academy of Nurse Practitioners. You can find Kristin on LinkedIn for more information.

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