Boys and girls who diet to lose or maintain weight may actually be doing the reverse, according to researchers at Brigham and Women's Hospital (BWH), a teaching affiliate of Harvard Medical School in Boston in the US.
A new study in the October issue of the journal Pediatrics showed that frequent dieting among children aged nine to 14 was not only ineffective, but appeared to result in weight gain in the long term.
"Our nationwide study found that as many as one in four American children under the age of 14 were dieting," said Alison Field, a BWH researcher. "Given the alarming increase in the percentage of children who are overweight, we felt it was important to understand whether dieting, which is common, particularly among girls, was helpful or actually contributing to the obesity epidemic."
The prevalence of overweight and obese children has increased by 100 per cent since the 1980s. Americans spend about $33 billion a year on weight loss products and services, however, only about one in five adults follow recommended diet guidelines, possibly explaining why most people fail to maintain long-term weight control. It now appears that casual dieting may be unsuccessful in children as well.
The research team found that about 30 per cent of the girls and 16 per cent of the boys were dieters at the start of the study in 1996. During the three years of follow-up, in which researchers sent 16,882 participants annual questionnaires about dieting, weight change, and exercise and eating habits, Field and colleagues found that although children who said they were dieters reported being more active and eating fewer calories than their peers, they gained more weight that non-dieters.
Field cited the case of a 14-year old girl who was a frequent dieter but gained about two pounds per year more than other 14-year old girls who did not diet. Girls who dieted less often gained slightly less weight, but still significantly more than non-dieters.
"At a time when we need solutions to encourage healthy eating habits, it is troubling to see that dieting, which is often characterised by short-term and not necessarily healthy changes in eating, is so common," noted Field. "Our study found that dieting was counterproductive - children who dieted gained more, not less, weight than non-dieters."
Field and her team provided several possible explanations for the link. The most likely, they say, is that dieting may lead to a cycle of restrictive eating, followed by bouts of overeating or binge eating. The repeated cycles of overeating, between the restrictive diets, may be responsible for weight gain. The fact that dieters were more likely to binge eat than their non-dieting peers supports this hypothesis.
When BWH researchers studied the mothers of these children, they found that the behaviours or lifestyle factors associated with weight control, or lack thereof, were established by late adolescence. However, this latest research suggests that dieting behaviours may manifest themselves at a much younger age.
"It is becoming increasingly important for parents and physicians to intervene and break bad eating and weight control habits early on," said Field. "Although for children and adolescents who are overweight, diets carefully supervised by a clinician may be beneficial and appropriate, our results suggest that casual dieting to control weight loss in the long term is not only ineffective, it may actually promote weight gain."