Ghrelin, the Hunger Hormone: Could It Be the Key to Weight Loss?
Ghrelin Levels of Dieters and Gastric Bypass Patients
Ghrelin is a naturally occuring hormone. Blood levels of ghrelin are lowest just after eating and then start rising again during fasting. Research shows that ghrelin levels are higher in lean individuals compared to obese individuals.
In a study published in the New England Journal of Medicine, researchers compared the plasma ghrelin levels of 13 obese patients following a six-month low-fat, low-calorie diet to plasma gherlin levels of five gastric bypass patients. The researchers found an increase in plasma ghrelin levels among the dieters, who had lost weight. However, among gastric bypass patients who had lost even more weight, plasma ghrelin levels were 77% lower than a control group with normal weight, and 72% lower than a matched control group of obese people.
Part of Body’s Normal Adaptive Response
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. Hence, dieters who depend on willpower alone to lose weight often find that it eventually eludes them. Recent research also suggests that in addition to increasing appetite, ghrelin encourages the accumulation of abdominal fat.
Gastric Bypass May Inactivate Ghrelin Cells in Stomach
Gastric bypass surgery is sometimes recommended for people who are considered morbidly ]]>obese]]> (those who are more than 100 pounds over their ideal body weight). The procedure involves reducing the size of the stomach by sewing a portion of it shut. As a result, a person feels fuller sooner and eats much less. Researchers in the ghrelin study suggest that in addition to the reduced calorie intake in these people, there may be another mechanism that contributes to the success of gastric bypass surgery. They believe that the ghrelin-producing cells in the bypassed portion of the stomach may become inactive when they are no longer exposed to food.
Ghrelin and the Future of Weight Loss
Many researchers believe that ghrelin plays a significant role in the long-term regulation of body weight. They suggest that excessive production of ghrelin may be a factor in many cases of morbid ]]>obesity]]> . But what accounts for increasing rate of obesity in recent years? Are people simply producing more ghrelin?
Most nutrition and obesity 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 and sustainable 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, according to the experts, most people can achieve a healthful weight and body fat level by making permanent and palatable changes in their eating habits and getting regular exercise.
It’s possible that in the near future, drug companies will develop a drug that blocks ghrelin. This would help reduce excess hunger and weight gain. In the meantime, additional studies are being conducted in this exciting new branch of obesity research.
American Dietetic Association
American Obesity Association
Canadian Council on Food and Nutrition
Dietitians of Canada
American Dietetic Association website. Available at http://www.eatright.org/ . Accessed May 1, 2003
American Obesity Association website. Available at http://www.obesity.org . Accessed May 1, 2003
Basque Research. "Action Of Ghrelin Hormone Increases Appetite And Favors Accumulation Of Abdominal Fat." ScienceDaily 20 May 2009. 21 May 2009. http://www.sciencedaily.com¬ /releases/2009/05/090520055519.htm.
Cummings D, Weigle D, Fray R, et al. Plasma ghrelin levels after diet-induced weight loss or gastric bypass surgery. N Engl J Med. 2002; 346:1623-1630.
Ghrelin.Colorado State University website. Available at: http://www.vivo.colostate.edu/hbooks/pathphys/endocrine/gi/ghrelin.html . Accessed May 22, 2009.
Katsuki A, Urakawa H, Gabazza EC, Murashima S, Nakatani K, Togashi K, et al. Circulating levels of active ghrelin is associated with abdominal adiposity, hyperinsulinemia and insulin resistance in patients with type 2 diabetes mellitus. Eur J Endocrinol . 2004;151:573–577
Monti V, Carlson JJ, Hunt SC, Adams TD. Relationship of ghrelin and leptin hormones with body mass index and waist circumference in a random sample of adults. J Am Diet Assoc . 2006 Jun;106(6):822-8.
Last reviewed May 2009 by ]]>Maria Adams, MS, MPH, RD]]>
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