Researchers from the USA investigated plasma ghrelin levels after diet-induced weight loss or gastric bypass surgery.
Weight loss causes changes in appetite and energy expenditure that promote weight regain.
Ghrelin is a hormone that is known to increase food intake in rodents and humans.
It is hypothesized that, if circulating ghrelin participates in the adaptive response to weight loss, its levels should rise with dieting.
As the stomach primarily produces ghrelin, weight loss after gastric bypass surgery may be accompanied by impaired ghrelin secretion.
The team determined the 24-hour plasma ghrelin profiles, body composition, insulin levels, leptin levels, and insulin sensitivity in 13 obese subjects.
This was done before and after a 6-month dietary program for weight loss.
The 24-hour ghrelin profiles were also determined in 5 subjects who had lost weight after gastric bypass and 10 normal-weight controls.
Five of the 13 obese subjects who participated in the dietary program were matched to the subjects in the gastric-bypass group, and served as obese controls.
Plasma ghrelin levels rose sharply shortly before and fell shortly after every meal.
|Plasma ghrelin levels:|
Diet-induced weight loss: increased
Gastric bypass surgery: decreased
| New England Journal of Medicine |
The obese participants achieved a diet-induced weight loss of 17% of initial body weight. This was associated with a 24% increase in the area under the curve for the 24-hour ghrelin profile.
In contrast, despite a 36% weight loss after gastric bypass, the area under the curve for the ghrelin profile in the gastric-bypass group was 77% lower than in normal-weight controls. It was also 72% lower than in matched obese controls.
The authors found that the normal, meal-related fluctuations and diurnal rhythm of the ghrelin level were absent after gastric bypass.
Dr David E. Cummings, of the University of Washington, said on behalf of his group, "The increase in the plasma ghrelin level with diet-induced weight loss is consistent with the hypothesis that ghrelin has a role in the long-term regulation of body weight."
"Gastric bypass is associated with markedly suppressed ghrelin levels, possibly contributing to the weight-reducing effect of the procedure," he concluded.