Dieters now have another culprit to blame for not losing weight. Hormones may cause obese people to regain weight after dieting, according to a new study published in the New England Journal of Medicine.

The study attempts to show how hormonal changes could increase the appetite of an obese person after dieting over a period of time. The researchers from the University of Melbourne and Austin Health recruited 50 overweight or obese people to participate in the study. The participants had an average weight of 95 kg. They were then kept on 10-week restricted low energy diet. They lost about 14 percent of their body weight or 29 pounds. The participants also showed a change in their hormone levels which increased their appetites.

Results showed that the participants' hormone levels had not returned to its previous levels before the study started. The participants who lost weight eventually regained around 5 kg around that time. The researchers said that the hormone levels offered a possible explanation for the weight gain.

Professor Joseph Proietto, a senior author of the study, said the results only underscore how hard it really is to lose weight.

"Our study has provided clues as to why obese people who have lost weight often relapse. The relapse has a strong physiological basis and is not simply the result of the voluntary resumption of old habits," he said.

Although the study is small with only 50 subjects and 16 quit or did not lose the weight, it still shows how hormone levels had a significant impact on losing weight. Leptin, which falls when people lose weight, also increases appetite and slows down metabolism. A year after the weight loss diet, the leptin levels in the participants were still one-third lower than they were at the start of the study. Other hormones like ghrelin which stimulates hunger, had increased and had not stabilized after a year.

Obese people could ask for drugs to restore their hormone levels after dieting but researchers are still looking for solutions to go the pharmaceutical route. What this study proves is that there needs to be more research into obesity, and blaming obese people for their lack of willpower is damaging.

"We need more knowledge," Dr. Jules Hirsch of Rockefeller University said. "Condemning the public for their uncontrollable hedonism and the food industry for its inequities just doesn't seem to be turning the tide."