BINGE eating, starvation diets, self-induced vomiting and laxative abuse are at least partly to blame for the epidemic of obesity among young women, according to Australian research that shows being overweight increasingly goes with such behaviour.

Rates of obesity and disordered eating each increased in the decade to 2005, but the chances of suffering both at the same time increased even faster, said Phillipa Hay, a professor of mental health at the University of Western Sydney's medical school and a leader of the 6000-person study.

The finding suggested standard weight control messages - eating moderately and exercising - were likely to miss the mark for a generation of women in whom drastic eating behaviour, driven by body image worries, was already entrenched. Instead, doctors should quiz overweight people directly about whether they ever binged or purged, and offer psychological support if this was the case.

"People often have a stereotype around eating disorders of the very thin girl with anorexia," Professor Hay said. But practices such as gorging, purging and diet pill or laxative abuse more usually affected people whose weight was normal or too heavy.

The study found one in 30 adults was now obese and also eating in a seriously disordered fashion - a more than four-fold increase over the 10 years. Although younger women were still most likely to be affected, the combination was also on the rise among men and across all age groups. Binge eating - defined as out-of-control excessive consumption - was most common, followed by diets that involved eating almost nothing.

"We know weight and body image concerns are rising and of significant importance to young people," Professor Hay said, and this drove them to extreme weight control efforts. But disordered eating made weight loss less likely, and unrealistic objectives - in which anything short of thinness was considered failure - meant obese young women might miss out on the health benefits of modest weight loss, such as improvements in blood pressure or insulin resistance.