Dieting woes tied to hunger hormone. (Biomedicine).

The latest findings on the hormone ghrelin may help explain why dieters find it so tough to keep off weight they've lost. Discovered in 1999, this hormone may also account for the frequent success of a last-ditch surgical strategy to beat obesity.

A growing amount of data suggests that ghrelin is the signal that makes people feel like eating (SN: 2/16/02, p. 107). The concentration of ghrelin in a person's blood rises rapidly right before a meal and falls once food is eaten.

In the May 23 New England Journal of Medicine, David E. Cummings of the University of Washington in Seattle and his colleagues report that obese people who followed a 6-month diet program and lost a significant amount of weight showed greatly increased ghrelin concentrations in their blood. This alteration in body physiology--and the hunger pains that presumably follow--contributes to post-diet weight gain, suggest the researchers.

The team also examined five obese people who had undergone gastric-bypass surgery. This drastic intervention, which shrinks the volume of the stomach and forces people to eat smaller meals, often leads to dramatic weight loss. Physicians have been puzzled by a secondary effect of the surgery: It seems to dull the appetite.

Cummings's team found that the ghrelin in the blood of people who had had the surgery had plummeted from normal concentrations and didn't fluctuate before and after meals. The researchers suggest that the surgery disrupts the stomach's normal ghrelin secretion.

"Our data represent the first indirect evidence in people that decreasing endogenous ghrelin might diminish appetite," says Cummings. This finding is sure to encourage drug companies that already are seeking drugs that suppress appetite by interfering with ghrelin activity.--J.T.