Hormones fight dieters' weight loss

VICTORIA, Australia, Oct. 26 (UPI) -- Weight gain among obese people after dieting is due to hormones fighting weight loss, not dieters returning to old eating habits, Australian researchers say.

The findings, published in the New England Journal of Medicine, suggested the high rate of relapse among obese people who have lost weight has a strong physiological basis and is not simply the result of the voluntary resumption of old habits, MedPage Today reported.

Joseph Proietto of Heidelberg Repatriation Hospital in Australia and colleagues said studies showed restricting calories can lower levels of the hormones leptin, which tells the brain the body is full, and ghrelin, which stimulates hunger.

Proietto and colleagues enrolled 50 overweight or obese patients in a 10-week weight-loss program that involved a very low-calorie diet, and tested levels of leptin, ghrelin and numerous other hormones at baseline, 10 weeks, and 62 weeks. They also questioned study participants about their appetites.

At the end of 10 weeks the participants had lost about 30 pounds and there were significant reductions in leptin, peptide YY, cholecystokinin, insulin and amylin -- while there were significant increases in levels of ghrelin, gastric polypeptide and pancreatic polypeptide, the study said. The dieters were also significantly hungrier, the study said.

"In obese persons who have lost weight, multiple compensatory mechanisms encouraging weight gain, which persist for at least one year, must be overcome in order to maintain weight loss," the study author wrote in the study.