Hair loss that results from weight loss is a temporary condition that occurs when a person loses weight through restrictive dieting or weight loss surgery. Stress on the body or nutrient deficiencies may be the cause.

This type of hair loss is generally known as telogen effluvium, and it is a common cause of hair loss. It typically occurs about 3–4 months after rapid weight loss and lasts for up to 6 months.

Not all hair that falls out is hair loss. It is normal to lose about 50–100 hairs per day, according to the American Academy of Dermatology. This is known as hair shedding.

During telogen effluvium, however, much more hair falls out.

Some causes of telogen effluvium can include:

  • losing a significant amount of weight
  • giving birth
  • having high levels of stress
  • having high fever
  • undergoing surgery
  • experiencing illness, particularly with high fever
  • stopping birth control pills

Telogen effluvium generally subsides within 6–9 months as the body adjusts to the changes.

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Telogen effluvium following weight loss is sometimes the result of nutrient deficiencies in the diet and the cumulative effects of weight loss on the body. This is particularly the case if the weight loss is due to crash dieting, weight loss surgery, or restrictive dieting.

Proper nutrition is vital to the formation of healthy hair shafts and the promotion of hair growth. Some studies suggest that diets low in iron and zinc may be more likely to induce hair loss. Other nutrients that may affect hair growth include fatty acids, selenium, and vitamin D.

Hair shafts undergo several cycles during their lifetime. These are as follows:

  • The anagen phase: This occurs when hair is growing and can last for several years.
  • The catagen phase: This is a short transitional phase of a few weeks.
  • The telogen phase: This is a rest phase of 3–4 months. At the end of this phase, the hair will fall out, and new hair will grow in the follicle.

Hair loss happens when stress on the body triggers the hairs to stop growing and enter the catagen phase too early. They will go on to the telogen phase and fall out prematurely.

Weight loss surgery

Although weight loss surgery can lead to reduced overall weight, it can also cause nutrient deficiencies that may lead to hair loss.

For example, one 2018 study involving 50 people who underwent sleeve gastrectomy observed hair loss in more than half.

Also, one 2021 study involving 112 women who underwent sleeve gastrectomy found that nearly 75% of them experienced hair loss. Of those who reported the condition, nearly 80% said that it started 3–4 months after surgery.

Hair loss due to weight loss is neither dangerous nor permanent. Generally, the body adjusts within a few months, and hair production resumes.

However, the nutrient deficiencies of a restrictive weight loss regimen can be damaging. For example, reducing the amount of iron in the diet can lead to iron deficiency anemia, which has several serious health complications.

Iron deficiency anemia can lead to:

Additionally, severe calorie restriction can lead to malnutrition and accompanying issues, such as decreased muscle function, cardiorespiratory problems, stomach issues, suppressed immunity, and depression and anxiety.

Telogen effluvium after weight loss can be the result of nutrient deficiencies or losing a lot of weight too quickly.

Prevention and treatment of telogen effluvium focus on proper nutrition and diet. Maintaining a balanced diet while avoiding crash diets and quick fixes is important to long-term weight loss success as well as avoiding telogen effluvium.

If someone is already experiencing telogen effluvium but is no longer trying to lose weight, they will most likely find that the condition resolves in time once they address their nutrient deficiencies through diet and, if necessary, supplementation.

A person should look for a paced, balanced diet that provides the essential micronutrients and macronutrients that the body needs each day to function.

Individuals should consult a licensed nutritionist if they are unsure what the proper levels of these micronutrients and macronutrients are.

If following a limited diet, be sure to include foods rich in iron and zinc. Look for:

  • shellfish
  • seeds
  • nuts
  • eggs
  • dairy
  • legumes
  • spinach
  • quinoa
  • turkey
  • broccoli
  • fish
  • cashews
  • chicken

Hair loss after weight loss is a common occurrence that may be the result of stress on the body or nutrient deficiencies.

Experts generally refer to this as telogen effluvium. Telogen effluvium begins about 3 months after the initial weight loss.

The condition is usually the result of nutrient deficiencies that arise from severely restrictive dieting or weight loss surgery. It will generally resolve within about 6 months as the body adjusts to the weight loss.

To treat telogen effluvium, a doctor may recommend adjusting the diet to add iron, zinc, and other essential nutrients if a person has a clinical deficiency. At present, there is a lack of research to support the use of supplementation to treat telogen effluvium if a person does not have a nutrient deficiency.