Risk factor: Anorexia nervosa

Having an eating disorder, like anorexia nervosa, can increase your risk of osteoporosis and broken bones.

If you have low body weight due to an eating disorder, and especially if you have gone without menstrual periods for months or years, you may well have low bone density and be at risk of fractures.

Many people with anorexia nervosa (and to a lesser extent bulimia nervosa) will have low bone density and consequently reduced bone strength and their risk of breaking a bone (fracture) is increased.

The low bone density in anorexia nervosa has several causes.

The body changes its hormone production in response to low body weight and these changes can affect bone density. Levels of insulin-like growth factor I (IGF-1), a hormone related to “growth hormone” and levels of oestrogen are reduced (which may cause women to stop having periods), and levels of cortisol (a steroid) are increased.

Also, poor nutrition and reduced muscle mass contribute to low bone density. Similarly, low hormone levels, weight loss and malnutrition may be responsible for the low bone density found in men with the condition.

Should people with anorexia nervosa have a bone density scan?

Your doctor or specialist may refer you for a DXA (dual energy x-ray absorptiometry) bone density scan, to establish if you have low bone density and may be at higher risk of fracture. A scan can help you and your doctors to understand if you are developing problems with your bones, and what can be done to reduce your risk of broken bones.

Should people with anorexia nervosa take osteoporosis drug treatments to strengthen their bones?

The best treatment for low bone density in anorexia nervosa is treatment of the underlying eating disorder, to restore body weight and hormones to normal. Effective treatment of eating disorders usually needs experienced help and support from a multidisciplinary team. An eating disorders team includes nursing and medical staff, psychiatrists, family therapists, psychologists and a dietitian.

Vitamin supplements may also be recommended, as adequate amounts of calcium and vitamin D are required for bone health. Some studies have tried using combined contraceptive pills to replace oestrogen and improve bone density. This approach has not however been shown to be effective because the pills can reduce growth factor (IGF-1) levels. Oestrogen skin patches may be a more effective treatment because they do not affect IGF-1 levels. The National Institute for Health and Clinical Excellence (NICE) have recommended in their clinical guideline on eating disorders (January 2004), that hormones should not be used to treat bone density problems in children or adolescents as this may interfere with their natural process of bone formation and growth.

Currently there are no approved treatments (including the use of hormones) to help with the bone loss associated with anorexia nervosa. Some small research studies have tried using bisphosphonate treatments, but not all of them have had positive results. Bisphosphonates are not generally recommended for women with anorexia nervosa due to the lack of data about both the benefits and also safety, particularly in women of child-bearing age. Occasionally a specialist may decide to treat a woman who has had spinal fractures with a bisphosphonate, but these decisions need to be made on an individual basis. Another treatment approach currently being studied is to use oestrogen in combination with other hormones such as IGF-1 or DHEAS (a male hormone, which healthy women produce in small amounts). This is because the low bone density in anorexia nervosa is caused by several hormone imbalances. Combined hormone treatment may therefore be a promising approach, although more research is needed before it can be recommended.

What about over-exercise?

Although regular exercise is known to be protective for bone density, excessive exercise particularly if body weight falls and loss of normal periods occurs, will affect bone in a similar way to the effect of anorexia nervosa. The intensity of exercise should be reduced and, if possible, calorie intake increased until body weight improves.

For those recovering from anorexia nervosa, advice about suitable activity levels and exercise should be sought from the team who is treating them and where ever possible under the direct supervision of a physiotherapist. The level of activity and exercise advised will depend on how stable an individual’s medical condition is currently, how well they are maintaining their target weight and whether dietary intake is sufficient to support an increased activity level. A graduated exercise programme including advice and information on how to exercise in a healthy way is recommended.

Anorexia nervosa is a complex medical condition and recovery may take many years. A significant number of people will continue to have lower bone density and the long-term effects on bone will be related to the severity and duration of their illness. Therefore, early diagnosis of anorexia nervosa and treatment is the most important factor affecting an individual’s prognosis and future bone health.

What else can people with anorexia nervosa do to prevent osteoporosis and fractures?

Other general lifestyle factors which can help to maintain healthy bones are avoiding smoking and keeping alcohol consumption within the recommended limits.

Useful download: Anorexia Nervosa and Osteoporosis Fact Sheet August 2014

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