Study shows why its hard to keep weight of

But now a group of Australian researchers have taken those investigations a step further. They recruited healthy people who were either overweight or obese and put them on a highly restricted diet that led them to lose at least 10 per cent of their body weight. They then kept them on a diet to maintain that weight loss. A year later,researchers found metabolism and hormone levels had not returned to the levels before the study started.

The study,being published Thursday in The New England Journal of Medicine,is small and far from perfect,but confirms their convictions about why it is so hard to lose weight and keep it off. Researchers not involved in the study cautioned that it had only 50 subjects,and 16 of them quit or did not lose the required 10 per cent of body weight. And while the hormones studied have a logical connection with weight gain,the researchers did not show that the hormones were causing the subjects to gain back their weight.

Nonetheless,said Dr Rudolph Leibel,an obesity researcher,while it is no surprise that hormone levels changed shortly after the participants lost weight,what is impressive is that these changes dont go away.

Dr Stephen Bloom,another researcher,said the study needed to be repeated under more rigorous conditions,but added,It shows something I believe in deeply it is very hard to lose weight. And the reason is that your hormones work against you.

In the study,Joseph Proietto and his colleagues at the University of Melbourne who weighed an average of 209 pounds. At the start,his team measured the participants hormone levels and assessed their hunger and appetites after they ate a boiled egg,toast,margarine,orange juice and crackers for breakfast. The dieters then spent 10 weeks on a very low calorie regimen intended to makes them lose 10 per cent of their body weight. In fact,their weight loss averaged 14 per cent. As expected,their hormone levels changed in a way that increased their appetites,and indeed they were hungrier than when they started the study.

They were then given diets intended to maintain their weight loss. A year after the subjects had lost the weight,the researchers repeated their measurements. The subjects were gaining the weight back despite the maintenance diet on average,gaining back half of what they had lost.