In some cases, weight loss can lead to side effects, including hair loss.
Your body is sensitive to nutrient deficiencies, stress, and hormonal changes — all of which can happen as a result of rapid weight loss, restrictive diets, or weight loss surgery.
This article explains why some people experience hair loss after weight loss and discusses ways to treat and prevent the issue.
Hair loss during weight loss is commonly caused by nutrient deficiencies as well as other effects sudden and rapid weight loss can have on your body.
For example, sudden weight loss and restrictive diets have been linked to a condition known as acute telogen effluvium (TE), one of the most common causes of widespread hair loss on the scalp (
Typically, TE occurs around 3 months after a triggering event like rapid weight loss and lasts about 6 months.
Weight loss and nutrient deficiencies associated with restrictive diets are also linked to other types of hair loss. These include chronic TE, which lasts longer than 6 months, and androgenic alopecia, also known as male or female pattern baldness (
Here are some causes of hair loss related to diet and weight loss.
The link between crash dieting and hair loss has been documented in research as far back as the 1970s (
Your hair needs adequate calories and nutrients to grow properly. So, when your body doesn’t receive what it needs, side effects like hair loss can occur.
Many studies have linked hair loss to rapid weight loss, calorie restriction, nutrient deficiencies, and psychological stress — all commonly in people who are following crash diets.
For example, a 2015 study in 180 women with diffuse hair loss found that the most common causes of hair loss were iron deficiency and psychological stress. In eight of the cases, crash diets were the cause (
Poorly planned diets, such as crash diets, can lead to deficiencies in essential fatty acids, zinc, protein, and overall calories, all of which can lead to hair loss (
Very low protein diets
Amino acids, the building blocks of protein, are essential for hair growth. That’s because amino acids are necessary for the production of keratin, the main structural protein of hair.
Protein malnutrition — when your body doesn’t get enough protein — can result in hair loss. Thus, if you’re following a low calorie weight loss diet that doesn’t contain enough protein, you may experience hair loss as a result (
When your protein needs aren’t met, your body prioritizes important protein-dependent functions like tissue repair, digestion, pH and water balance regulation, and hormone production. Because hair growth isn’t essential to keep you alive, hair loss may occur (
Additionally, deficiencies in specific amino acids, such as histidine, leucine, valine, and cysteine, are common in people with hair loss.
In a study in 100 people with hair loss, researchers observed histidine and leucine deficiencies in large percentages of participants across several types of alopecia, including androgenic alopecia and TE (
The study also found that valine and cysteine deficiencies were common among the participants (
Weight loss surgeries
Weight loss surgery is associated with rapid weight loss and commonly causes deficiencies in protein, vitamins, and/or minerals, which in turn can spark hair loss (
For example, a 2018 study that included 50 people who underwent sleeve gastrectomy, a surgical procedure that removes a large portion of the stomach, observed hair loss in 56% of the participants. Hair loss was more common in women (
Notably, the participants with hair loss had much lower levels of zinc and vitamin B12 both before and after surgery (
In a 2020 study in 112 women who had undergone sleeve gastrectomy, 72% of participants experienced hair loss after surgery. In 79% of those who reported hair loss, the loss started 3–4 months after surgery and lasted an average of 5.5 months (
In addition to reducing stomach capacity, some types of weight loss surgery allow food to bypass part of the intestines, leading to malabsorption of nutrients and increasing the risk for deficiencies (
Just like crash diets, restrictive diets that cut out entire food groups can cause hair loss as a result of nutrient deficiency or stress.
Deficiencies in iron, zinc, protein, selenium, and essential fatty acids have all been linked to hair loss (
Very low calorie diets have been shown to cause hair loss as well (
Major stress, which sometimes comes along with restrictive dieting, has also been linked to hair loss (
Hair loss during or after weight loss can be caused by nutrient deficiencies, rapid weight loss, and stress.
Hair loss itself isn’t dangerous, but the underlying causes of hair loss after weight loss can be.
For example, nutrient deficiencies and extreme calorie restriction can lead to serious health consequences like iron deficiency anemia, muscle loss, and more.
Besides potentially causing hair loss, iron deficiency anemia can lead to impaired brain function, infertility, heart conditions, depression, and altered immune system function (
Calorie and protein restriction can also cause dangerous side effects, including decreased muscle function, heart problems, intestinal issues, decreased immune function, and increased risk of depression (
Other medical conditions, such as autoimmune conditions, can also cause hair loss. Therefore, it’s important to talk to a healthcare provider if you’re experiencing hair loss, because it might not be related to weight loss.
Although hair loss itself is not dangerous, the underlying causes can be. If you’re experiencing hair loss, it’s important to consult your healthcare provider to rule out an underlying medical condition.
As mentioned, hair loss during weight loss can be caused by nutrient deficiencies or rapid weight loss. As such, it’s important that you aim to lose weight in a healthy, sustainable manner.
In addition to potentially leading to hair loss, crash and restrictive diets can be harmful to mental health and are associated with weight regain (
Instead of a fad diet, choose a balanced diet that provides your body with the nutrients it needs to function optimally. Saying no to restrictive diets that promise rapid weight loss is essential for protecting your physical and mental health and reducing the risk of side effects like hair loss.
Additionally, if you follow a dietary pattern that restricts many foods — such as a vegetarian or vegan diet, which may be low in hair loss-associated nutrients like iron and zinc — make sure to include nutrient-dense foods and supplement with nutrients your diet lacks (
If undergoing weight loss surgery, ensure that your levels of nutrients like zinc, iron, and vitamin B12 are optimal before the procedure, and supplement with nutrients recommended by your doctor or dietitian afterward. This can help prevent surgery-related hair loss (
How to facilitate hair regrowth
If you’re experiencing hair loss, it’s critical that you identify the cause before you try to treat it.
Remember, hair loss can have many causes, not just rapid weight loss or nutrient deficiencies.
If the hair loss is caused by a deficiency in one or more nutrients like zinc or iron, correcting the deficiency or deficiencies may stop the loss and lead to hair regrowth (
If a restrictive or crash diet that’s not giving your body enough calories or nutrients is to blame, it’s essential to stop the diet immediately and begin fueling your body correctly with a balanced diet rich in nutrient-dense foods.
If you have a nutrient deficiency, food alone may not be enough to replenish your nutrient stores and a supplement may be necessary. However, research suggests that if you don’t have a nutrient deficiency, supplements might not benefit hair loss (
A healthcare provider can identify the cause of your hair loss and help you come up with a plan to get your hair growing again.
To prevent hair loss, avoid crash and restrictive diets, fuel your body properly, and supplement before and after weight loss surgery. Work with a qualified healthcare provider to identify the cause of hair loss and to find a plan to facilitate hair regrowth.
Hair loss during or after weight loss can be caused by a number of factors, including nutrient deficiencies.
However, hair loss can also be caused by underlying health issues, so it’s important not to self-diagnose your hair loss as weight loss-related.
Work with a qualified healthcare provider such as a doctor or registered dietitian to identify the cause of your hair loss and to come up with a treatment plan to facilitate hair regrowth.