Friday, March 19, 1999 Published at 10:17 GMT
Anorexia risk of moderate dieting
Exercise is better than dieting for the overweight, say doctors
Overweight teenagers should exercise rather than diet because even those who diet moderately are at huge risk of developing eating disorders, according to an Australian study.
Girls who go on severe diets are 18 times more likely to develop a disorder such as anorexia, say the researchers.
But those who diet moderately - a much larger number - are five times more at risk of suffering eating problems than the average child.
Two thirds of new cases of eating disorder are in girls who have dieted moderately.
Writing in the British Medical Journal, the researchers from Victoria, Australia, say dieting is the biggest risk factor for anorexia and bulimia.
Exercise and diet
Over a three-year period, they studied a group of 14 and 15 year olds - girls and boys - from 44 schools.
They measured their weight and height. They also asked them whether they dieted and how much they cut back their food intake.
They also asked how frequently they exercised.
In addition, the researchers evaluated the teenagers' mental health, assessing for common symptoms of psychiatric disorder.
Eating disorders are common in young girls.
In Britain, it is thought that up to 5% of girls are anorexic.
Both anorexia -self-starvation - and bulimia - binge eating and dieting - carry a health risk.
Up to 20% of anorexics die within 20 years of the disease starting.
The researchers say 8% of 15-year-old girls in their study dieted severely and 60% dieted moderately.
Severe dieters were 18 times more likely than other girls to develop a new eating disorder within six months than those who did not cut back on food.
Moderate dieters were at a five times higher risk.
The girls' mental health was also a risk factor.
Those with high levels of mental health problems were up to seven times more likely to develop eating disorders than the average teenager.
The researchers say the risk of becoming anorexic and bulimic is so high for girls because they are more likely to diet and suffer mental health problems than boys.
Evidence shows that exercise can also be a danger factor for eating disorders.
But the researchers say they believe the risks are much lower than dieting and tend to be associated with specific sports - such as gymnastics - which emphasise thinness.
They think teenagers with weight problems would be better advised to do daily exercise to keep their weight down than to diet.
They conclude: "Dieting is the most important predictor of new eating disorders.
"Differences in the incidence of eating disorders between sexes were largely accounted for by the high rates of earlier dieting and psychiatric morbidity in the female subjects.
"In adolescents, controlling weight by exercise rather than diet restriction seems to carry less risk of development of eating disorders."
Research shows children are not doing as much exercise as they did in the past because of lack of space to play and parents' fears about letting their children out on the streets.
A government report this week says teenage girls are particularly reluctant to do sport.
Caroline Green of the Centre for Eating Disorders said children needed to be encouraged to adopt a healthy attitude to exercise and eating from an early age.
Many girls put looking good in their sports gear above exercise.
This meant that if they were overweight they would be more reluctant to exercise.
"We feel that because of the thin culture of the 1990s more and more very young people start on diets which seem harmless.
"Before they know it they are unable to stick to it and in order to maintain their weight they make themselves sick.
"This can be the first step to an eating disorder."
She added that mental health and diet were linked.
"The mind and the body are interlinked. Girls tend to associate success at dieting with success in other areas of their lives."
The Centre is setting up a national helpline for people with eating disorders after Easter.
This follows a flood of calls to its first Christmas helpline.