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.