11th February, 20227 min read

How weight loss can cause hair loss – and what to do about it

Medical reviewer:
Dr Ann Nainan
Dr Ann Nainan
Dr Adiele Hoffman
Dr Adiele Hoffman
Author:
Amelia Glean
Amelia Glean
Last reviewed: 11/02/2022
Medically reviewed

All of Healthily's articles undergo medical safety checks to verify that the information is medically safe. View more details in our safety page, or read our editorial policy.

Weight loss and hair loss

It’s normal to shed a bit of hair every day, especially when you brush or wash it. But if you’ve noticed more of your hair falling out than usual, you’re probably wondering what’s causing it.

Intentional weight loss could be a reason for your hair loss, especially if you’ve:

  • lost a lot of weight in a short space of time
  • been following a very low calorie diet (VLCD) – including following a VLCD diet under your doctor’s supervision
  • been cutting out whole food groups
  • had weight loss surgery, such as a gastric band fitted
  • become underweight
  • been diagnosed with, or think you might have, an eating disorder

Losing your hair can be upsetting, but the good news is that hair loss caused by weight loss, or a nutrient deficiency, is usually temporary. In most cases, your hair will start to go back to normal within 3 to 6 months – once your body has adjusted to the weight loss, and as long as you’re also getting the right nutrients by eating a healthy, balanced diet.

It’s also important to know that if you’re losing hair and losing weight, it may be due to another underlying medical condition, such as having an overactive or underactive thyroid. Read on to learn what you can do about intentional weight loss and hair loss, and when to see a doctor.

How does weight loss cause hair loss?

If you’ve been trying to lose weight or you’ve lost weight quickly, your hair loss may be due to a condition called telogen effluvium. This is when something disturbs your hair’s normal growth cycle and pushes more hairs into the resting, or ‘telogen’ phase, leading to more of your hairs falling out than usual. It’s often triggered by a shock or a big stress on your body – this can include intentional weight loss.

You might also be losing hair because your body isn’t getting the nutrients it needs, for example if you’re following a diet that involves eating very few calories or cutting out whole food groups. This sort of restrictive diet can mean your body isn’t getting enough energy or the right nutrients to function properly. In this case, whatever energy is available is sent to your body’s most vital organs instead, and away from less important areas like your hair follicles, which may affect the health of your hair.

How does weight loss surgery cause hair loss?

Hair loss is also a common side effect of rapid weight loss following weight loss surgery, such as a gastric bypass, and can start from about 3 months after your operation.

Both the surgery itself, which puts a big stress on your body, and the weight loss that follows can be a cause of hair loss. But as with other causes of telogen effluvium, your hair will usually grow back within 6 months from this time. Be careful to follow the meal plans and medication suggested by your doctor to ensure you’re getting enough calories and nutrients, while allowing your stomach and intestines to recover.

What to do about hair loss caused by weight loss

Good health and nutrition can help you both avoid and recover from hair loss caused by weight loss. And there are things you can do to help you maintain a healthy weight and diet.

Improve your nutrition

Going on a restrictive or ‘extreme’ diet is a common way to lose weight quickly by reducing how much you eat and avoiding certain food groups. But this can lead to malnutrition and hair loss.

Common restrictive diets include:

  • ketogenic (‘keto’) diet – you eat only low-carbohydrate, high-fat meals
  • intermittent fasting – you eat only at a certain time of the day
  • very low calorie diet (VLCD) – you eat only liquid foods, soft foods or very small portions. This type of diet should only be followed under medical advice – it’s often prescribed after weight-loss surgery

If you’ve been restricting what you eat and you’re worried that it’s having an effect on your nutrition and hair, try switching to a more balanced diet. This will help ensure you’re getting the vitamins and minerals your body needs to function properly, including for maintaining healthy hair.

If you’ve been restricting your diet, it could mean your body isn't getting the nutrients (particularly protein) it needs to grow your hair, leading to hair thinning or loss. Being underweight is a risk factor for getting a lack of nutrition. One way to check whether you might be underweight is to check your Body Mass Index (BMI). This takes your height and weight, gives you a score and tells you whether you’re potentially over or underweight. You can calculate your BMI here. Bear in mind BMI doesn’t take into account your muscle, fat and bone, alongside weight. So if you’re worried about your weight or how this might be affecting your hair, it’s always best to talk to your doctor.

If you’ve made changes to your diet and you still need to lose weight to get to a healthy size, you could try being more active. If you need a little help with this, our 28-day in-app ‘Get Fitter’ plan (currently available on iOS only) is brimming with all the latest hacks on how to work more exercise into your day.

healthy diet

Consider supplements

A restrictive diet can lead to low levels (deficiencies) of essential vitamins and minerals, including ones you need for healthy hair. For example, iron, B12 or folate deficiencies can affect hair growth. Your doctor can check for nutrient deficiencies with a blood test and recommend suitable supplements if needed.

Nutrient deficiencies can also happen if your body struggles to absorb nutrients from food – which can happen after weight-loss surgery. In this case, your doctor may recommend a multivitamin that contains calcium, iron and vitamin B12.

When to see a doctor

Hair loss after weight loss is usually temporary, and your hair will generally go back to normal after a few months. But it’s still best to speak to a doctor if you’ve lost weight or you’re following a restrictive diet and you’re getting hair loss, so they can check what’s causing it.

You should also see a doctor if you think your weight loss might be driven by an eating disorder, such as anorexia nervosa. They can help you get the support you need to tackle your condition, and help balance out your diet again.

As well as a low body weight (BMI) and hair loss, the common symptoms of an eating disorder include:

  • restricting your diet because you’re scared to gain weight, even though you’re underweight
  • missing meals, not eating much or avoiding certain foods, which can get in the way of your social life
  • taking medicines to reduce your hunger (appetite suppressants) or make you go to the toilet more (laxatives)
  • binge eating large amounts of food and then making yourself sick

Remember, losing weight isn’t the only reason you might notice hair loss – read about other possible causes of hair loss and hair loss treatments.

You should also see a doctor if you’ve lost weight without trying to. There are some medical conditions that can cause both hair loss and weight problems, including thyroid disorders for example, so your doctor will be able to help look into why you’ve lost weight.

Or try our Smart Symptom Checker to get more information about your health.

Your health questions answered

Can too much exercise cause hair loss?

Answered by: Healthily’s medical team

“What amounts to too much exercise means different things to different people. There’s no evidence that exercise in general causes hair loss, but if you start working out excessively (for more than 3 hours a day), or lose weight very quickly as a result, it’s thought it could put your body under stress and trigger a type of hair loss called telogen effluvium. This is the same type of hair loss triggered by intentional weight loss after following a restrictive or extreme diet. But there’s little medical research to back this up, so if you’re worried about hair loss it’s best to speak to a doctor.”

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