Hormone injection key to fighting obesity

Every dieter knows that shedding excess pounds is far simpler than maintaining a new slimline self. Now Obesity specialists at Columbia University claim to have remedied the problem. They say that by restoring the hormone leptin to its level before weight loss, patients maintained their slim figures.

Leptin is thought to play a key evolutionary role in survival by signalling how much fat the body stores. As fat is lost, the level of leptin declines reducing energy expenditure to conserve calories.

The effect is the reverse of what dieters want. The reduction in energy expenditure means fewer calories are burnt. Dieters on the same calories gain weight.

In preliminary trials in 10 patients on a diet, three of whom were of normal weight and seven obese, researchers found that twice daily injections of leptin helped maintain low weight. The experiment was run for seven weeks. Writing in the Journal of Clinical Investigation, the authors, led by Michael Rosenbaum, say that the body interprets the weight-reduced state as one of "relative leptin insufficiency".

"This decrease in energy expenditure is of sufficient magnitude to account - in part - for the very high recidivism to obesity in otherwise successfully weight-reduced subjects."