Anorexia and osteoporosis

Having an eating disorder, like anorexia nervosa, can increase your risk of osteoporosis and broken bones. The information on this page explains why this might happen, and what you can do to help strengthen your bones.

What is anorexia?

Anorexia nervosa is an eating disorder that causes low body weight and an intense fear of weight gain. Affected people limit the amount they eat and drink, even though they are underweight and not getting the food they need.

Anorexia is most common in young women. But at least 1 in 10 people with an eating disorder – possibly as many as 1 in 4 – are men.

There are other types of eating disorder, such as bulimia nervosa. People with bulimia follow a pattern of 'bingeing' (eating lots of food) and then 'purging', either by making themselves sick, taking drugs such as laxatives, or doing lots of exercise to help them lose weight. Bulimia doesn’t always cause severe weight loss.

Does anorexia cause osteoporosis and fractures?

It can do, as it can affect healthy bone growth and lead to low bone density. If you have low bone density, your bones may be weaker and more likely to break.

Eating disorders often develop in teenagers. Childhood and the early adult years are a very important time for our bones. They quickly get bigger and stronger as you grow, especially during puberty. Changes in your levels of sex and growth hormones during these years play an important part in building healthy bones.

Your bones usually reach their maximum strength around the end of your 20s. This is called your ‘peak bone mass’ – and it's affected by what happens in this growth period.

How might anorexia affect my bones?

If you have anorexia you probably will have low bone density. (This is also possible, but less likely, if you have bulimia.) There are a number of reasons for this.

• Your level of oestrogen may drop. Oestrogen is a hormone that’s important for healthy bones.
• Your level of insulin-like growth factor 1 (IGF-1) may drop. IGF-1, a hormone related to growth hormone, is important for healthy bone growth during puberty, and for bone health in general.
• Your level of cortisol may increase. High levels of cortisol, a steroid hormone, can affect your bone health.
• Your bones may not get the nutrition they need.
• The size and strength of your muscles may decrease. This means the bones experience less force from your muscles and may become weaker.

If your anorexia has caused low bone density, your bones may be weaker and you may be more likely to break a bone.

What about men?

Anorexia is often not spotted or diagnosed as early in men, which means both the eating disorder and any impact on your bone health may go untreated for longer. It’s also common for boys and young men with anorexia to combine eating very little with doing lots of exercise, which can also reduce hormone levels and bone strength.

How will I know if I'm at risk?

If you’re underweight, you are very likely to have low bone density – especially if you used to have monthly periods but haven’t had one for months or years. This is because your periods stopping can be a sign of low oestrogen, which can affect your bones.

Your risk of fractures will also depend on other things, such as your age (if you are over 50) and whether you've already broken bones easily.

Should I have a bone density scan?

Not everyone with anorexia needs a bone density scan. If you’ve had anorexia for a long time, then it may be helpful. If you’re over 50, you may have a scan as part of a general bone assessment. This is recommended for any older person with risk factors for osteoporosis. To find out more about having your bone health checked, read our information on fracture risk assessments.

Should I take an osteoporosis drug?

If you have anorexia, the best treatment for low bone density is treatment of the eating disorder itself. This will restore your body weight and normal hormone levels. It usually takes expert help and support from an eating disorders team to treat an eating disorder effectively.

You may be advised to take supplements, as adequate amounts of calcium and vitamin D are needed for bone health. There is some evidence that bone density recovers better in people with good vitamin D levels. However, on its own, this won’t make your bones stronger.

Drug treatment is sometimes used to improve bone density, although mainly in people over the age of 50.

If you’re under 50

If you’re a younger adult, your risk of breaking a bone is likely to be quite low, even if your bone density is low. You’ll probably only be offered a drug treatment if your bone density is very low, or you’ve already broken a bone.

If you are under 50 and need a drug treatment, the options include:

• oestrogen hormone skin patches
• contraceptive pills containing oestrogen
• drugs called bisphosphonates (although this is uncommon).

A bisphosphonate may be an option if you’re a woman over 18 years of age with anorexia, long-term low body weight, and low bone density for your age. However, it’s important to discuss the risks and benefits with your healthcare professional, particularly if you might want to have children in the future. This is because we don’t yet know for certain whether bisphosphonates might affect an unborn child.

If you’re a young adult, you should only be prescribed a drug treatment if you or your doctor have spoken with a hospital doctor who specialises in child and adolescent health (a paediatrician), or in hormones (an endocrinologist).

If you’re over 50

You're more likely to be recommended an osteoporosis drug if you’re over the age of 50. In older women, the first-choice treatment is likely to be a bisphosphonate drug such as risedronate.

Should I exercise less?

In general, regular exercise is very good for bone health and rarely causes broken bones, even if you have osteoporosis. But you should only exercise if your weight is medically safe and you’re consuming enough calories to support the activity.

People with anorexia often over-exercise to lose weight, but this could reduce hormone levels and make your bones weaker. So focusing on your recovery is the best thing you can do for your long-term bone health.

Ask your medical team about suitable levels and types of exercise. How much you’re advised to do will depend on:

• how stable your condition is
• how well you are keeping to your target weight
• whether you are eating enough to support exercise.

They’ll often recommend an exercise programme that starts off gently and slowly increases over time, along with advice and information on how to exercise in a healthy way.

If you often break bones or have had spinal fractures, then low-impact exercises may be safest for you.

We have lots of information about exercise, including our series of fact sheets and accompanying exercise films.

What else can I do to help my bones?

Other things that can help to maintain healthy bones include:

• avoiding smoking
• staying within the recommended limits for drinking alcohol.

Anorexia is a complex medical condition and it can take many years to recover. Your bone health will be at greater risk if you have severe or long-term anorexia. It’s important to get your eating disorder diagnosed and to start treatment for your anorexia as early as possible. This is the most important thing you can do for your overall health and wellbeing, including your bones.

You may find the following organisations helpful:

• Talk ED
• Beat
• National Centre for Eating Disorders

You can also contact our specialist Helpline nurses, for free, with any questions or concerns about bone health.

Content reviewed: February 2022