MEDICAL NEWS: WHY HIGH-PROTEIN, LOW-FAT AND LOW-CARBOHYDRATE DIETS SUPPRESS HUNGER

February 6, 2008 — Many popular diet plans are based on changing the proportion of carbohydrates, proteins and fats one ingests as a method to promote weight loss. There has been some controversy regarding the effectiveness of these diets, but a new study accepted for publication in the Journal of Clinical Endocrinology & Metabolism (JCEM)I>could shed light on potential mechanisms by which various diets promote weight loss.

This study examined the relative ability of different nutrient types to suppress ghrelin, which is secreted by the stomach and is the only known appetite-stimulating hormone. Circulating ghrelin levels increase shortly before meals and then decrease promptly after ingestion of food.

"We found that when fat is consumed, levels of ghrelin remain relatively high, which could in turn stimulate hunger," said Dr. Karen Foster-Schubert of the University of Washington School of Medicine in Seattle, Washington. "Protein consumption resulted in the greatest suppression of ghrelin over a long period and, interestingly, consumption of carbohydrates resulted in a strong ghrelin suppression initially, although subsequent ghrelin levels rebounded well above baseline."

In this study, subjects were given three beverages with widely varying compositions of macronutrients (carbohydrates, fats and proteins). Blood samples were taken before the first beverage was ingested and every 20 minutes for six hours thereafter. Researchers then measured the ghrelin levels in each sample.

"These findings open the door to future research on the effectiveness of varying methods of dieting," said Foster-Schubert. "Improving our understanding of the regulation of ghrelin by ingested macronutrients could facilitate rational design of weight-reducing diets."

Other researchers involved in this study include Joost Overduin, Holly Callahan and David Cummings of the University of Washington School of Medicine in Seattle, Washington; and Jianhua Liu, Bruce Gaylinn, Michael Thorner and Catherine Prudom of the University of Virginia in Charlottesville, Virginia.