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Ghrelin is a naturally occurring hormone. Blood levels of ghrelin are lowest just after eating and then start rising again during fasting.
According to researchers, the rise in ghrelin levels caused by an empty stomach and dieting is part of the body’s normal adaptive response. When we restrict our calories and/or lose weight, our bodies interpret this as famine. In response, a mechanism is triggered to keep our weight constant. Our metabolism slows down and we feel hungry, so we eat more. Dieters who depend on willpower alone to lose weight often find that it eventually eludes them. In addition to increasing appetite, ghrelin may also encourage the build up of abdominal fat.
Gastric bypass surgery is sometimes recommended for people who are morbidly obese. The procedure involves reducing the size of the stomach by creating a small pouch. As a result, a person feels fuller sooner and eats much less. In one small study, researchers found that ghrelin levels rise in people who are dieting. But, those who have undergone gastric bypass actually have lower amounts of ghrelin in their bodies, which seems to play a positive role in being able to lose weight.
Many researchers believe that ghrelin plays a significant role in the long-term regulation of body weight. They suggest that excessive production of ghrelin or a heightened sensitivity to this hormone may be a factor in obesity.
Although, it is important to note that most nutrition experts attribute the increasing rate of obesity to modern lifestyle factors, such as increased consumption of high-calorie foods and lack of regular exercise. Many people try to diet to lose weight, but do not make permanent changes in their eating and exercise habits. Since most dieting involves food and calorie-restriction, it is often unsuccessful simply because it is monotonous, restrictive, and causes hunger. But, most people can achieve a healthy weight and body fat level by making positive changes in their eating habits and activity level.
It is possible that in the near future drug companies will develop a drug that focuses on the role that ghrelin plays in the body. This drug could potentially help reduce excess hunger and weight gain. In the meantime, additional studies are being conducted in this branch of obesity research.
Eat Right—Academy of Nutrition and Dietetics
The Obesity Society
Dietitians of Canada
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Last reviewed April 2017 by Michael Woods, MD, FAAP Last Updated: 4/22/2015