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.

[New techniques in nutritional surveys and food educational programs: volumetric dietetics for portion size assessment]. / Tecniche innovative per la sorveglianza nutrizionale e l'educazione alimentare: la dietetica per volumi.

Data in literature show that body weight in adults and children seems to be related to portion sizes more than to food choices and people are more reluctant to give up favourite foods than to reduce portions. So several scientific societies in USA have recently emphastzied the need to select appropriate portion sizes. At the same time, studies on cognitive strategies show that the best method to help people to remember how much they eat is visualisation/comparison to tridimensional visual aids. So a new technique for evaluating portion sizes, based on comparison of portions to volume of usual objects (baseball, dice, deck of cards) appeared in the last years, in nutritional surveys and food educational projects. Our team, since 1990, appointed a volumetric assessment based on comparison of foods to the fist, palm, fingers of the examined subject; this system has been experienced with success for a long time both in individual dietetics and in food educational projects or surveys. Since the interest for this new technique is rising, the aim of this review is to introduce the method and to delineate the applications in nutritional surveys or educational projects in national and international literature. This method, simple practical and intelligible, seems to be addressed to a wide development in the future.