Skinny teenagers and girls suffering from anorexia could be seriously damaging their bones and increasing their risk of osteoporosis later in life.

The debate about underweight models has captured headlines but the International Osteoporosis Foundation (IOF) said little attention is given to the link between anorexia and osteoporosis or the long-term consequences of dieting during adolescence - the greatest period of bone growth.

“Anorexia is serious but not everybody realizes that it has a serious implication for bone health,” said Paul Spencer Sochaczewski, of the Swiss-based IOF.

Although the brittle bone disease usually occurs after the menopause, its seeds are sown much earlier in life.

Eating a healthy diet with enough calcium, vitamin D and proteins and building maximum bone growth during the teenage years can help cut of risk of osteoporosis decades later.

But it is also the age group when many girls begin dieting to keep down their weight.

“The age at which most women develop anorexia is during the teenage age years which is also when bones develop the fastest and they develop their peak bone mass. If they miss out on that they are going to be damaging their bone health in later life,” Sochaczewski told Reuters.

Anorexia can lead to estrogen deficiency and the cessation of menstrual periods. The IOF said the drop in estrogen in adolescence could contribute to bone density loss in the same way it does in older women after the menopause.

It estimates that anorexia patients who suffer from the illness for six years have an annual fracture rate seven times greater than a healthy woman of the same age.

“If they (young women) are not getting their maximum bone density at that time, they are setting themselves up for fractures later on in life,” he added.

An estimated one third of women over 50 years old will suffer from fractures due to osteoporosis, according to the IOF.

It added that an analysis of 60,000 men and women showed that the risk of hip fracture also doubled in people with a body mass index (BMI) of 20 compared to people with a BMI of 25. A 10 percent loss of bone mass can double the risk of vertebrae fractures.

BMI is calculated by dividing weight in kilograms by height in metres squared. A BMI of 20 or less is underweight, while 20-25 is normal.

Smoking and drinking heavily, low body weight and a family history of the illness are also risk factors for osteoporosis.