High glycemic index foods, overeating, and obesity

Objective. The prevalence of obesity has increased dramatically in recent y ears. However, the role of dietary composition in body weight regulation re mains unclear. The purpose of this work was to investigate the acute effect s of dietary glycemic index (GI) on energy metabolism and voluntary food in take in obese subjects. Methods. Twelve obese teenage boys were evaluated on three separate occasio ns using a crossover study protocol. During each evaluation, subjects consu med identical test meals at breakfast and lunch that had a low, medium, or high GI. The high- and medium-GI meals were designed to have similar macron utrient composition, fiber content, and palatability, and all meals for eac h subject had equal energy content. After breakfast plasma and serum concen trations of metabolic fuels and hormones were measured. Ad libitum food int ake was determined in the 5-hour period after lunch. Results. Voluntary energy intake after the high-GI meat (5.8 megajoule [mJ] ) was 53% greater than after the medium-GI meal (3.8 mJ), and 81% greater t han after the low-GI meal (3.2 mJ). In addition, compared with the low-GI m eal, the high-GI meal resulted in higher serum insulin levels, lower plasma glucagon levels, lower postabsorptive plasma glucose and serum fatty acids levels, and elevation in plasma epinephrine. The area under the glycemic r esponse curve for each test meal accounted for 53% of the variance in food intake within subjects. Conclusions. The rapid absorption of glucose after consumption of high-GI m eals induces a sequence of hormonal and metabolic changes that promote exce ssive food intake in obese subjects. Additional studies are needed to exami ne the relationship between dietary GI and long-term body weight regulation .