Effect of dietary glycemic index on food intake, adiposity, and fasting plasma ghrelin levels in animals

Background: An increase in lipid storage as a consequence of feeding animals with high-glycemic index (GI) diets has been observed by many authors. Ghrelin is one of the most important orexigenic hormones, and curiously, its fasting plasma levels are decreased in human obesity. Aim: As ghrelin secretion is affected by insulin concentration, we hypothesized that carbohydrates with different glycemic responses might influence fasting plasma ghrelin levels. Material and methods: Twenty rats were divided into two groups and fed ad libitum a low-GI or a high-GI diet for 21 days. Results: In rats fed a high- vs low-GI diet we observed: increased food intake (18.9+/-0.6 vs 16.4+/-2.0 g/day; p<0.01), increased weight gain (28.8+/-6.6 vs 16.4+/-6% of initial weight; p<0.01), higher relative weight of epididymal fat pads (1.7+/-0.4 vs 1.4+/-0.3%; p=0.05), but lower total fasting ghrelin levels (41.1+/-10.7 vs 59.5+/-9.8 pg/ml; p=0.05). Conclusions: Ghrelin appeared to be downregulated in rats fed a high-GI diet; this observation could be related to the higher food intake and fat mass observed in these rats and to the effects of insulin response on ghrelin levels.