NEW YORK (Reuters Health) - Once weight loss is achieved, restoring levels of leptin -- a hormone made by fat cells -- to pre-weight loss levels may be the key to keeping it off, according to results of a study released Thursday.
"Many people lose weight, but few manage to sustain their thinner selves," said Dr. Michael Rosenbaum from New York Presbyterian Hospital/Columbia University Medical Center in New York and first author on the paper.
"Attempts to keep weight off by lean or overweight individuals are met by potent physiological forces that all act together to favor the regain of lost weight," he explained. "Many of these forces are also turned on in humans and rodents who are unable to make leptin."
Rosenbaum and colleagues hypothesized that the human body sees the weight-reduced state as one of relative leptin deficiency, which favors weight gain.
To test their theory that low leptin levels induced by weight loss are to blame for weight rebound, they administered twice daily leptin injections to 10 people who had lost 10 to 12 percent of their weight as in-patients at Columbia Presbyterian Medical Center.
They found that most of the changes that oppose the maintenance of a reduced body weight were actually reversed once circulating levels of leptin were restored to levels that were present prior to weight loss.
The implications for weight management are potentially important, Rosenbaum told Reuters Health.
"Most current weight-loss medications act by increasing energy expenditure or decreasing appetite to levels that are abnormal for us and then only work for limited periods of time," the researcher explained.
"In contrast, therapeutics directed at the leptin signaling pathway may, pending longer studies, result in the restoration of these physiological processes to usual levels such that our bodies would work with us, rather than against us, in keeping the weight off," Rosenbaum predicted.
SOURCE: Journal of Clinical Investigation, December 1, 2005.