Metabolic responses to high carbohydrate breakfasts in obese patients with impaired glucose tolerance. Comparison of meals containing dairy products and fruits versus bread.

Carbohydrate (CHO) enriched diets can improve glucose tolerance in healthy subjects but have controversial effects in NIDDM patients. Their effects on glucose metabolism are not clearly established in obese patients with impaired glucose tolerance (IGT) and might depend on their glycemic index (GI). For that reason, we compared the metabolic responses to 2 isocaloric CHO rich breakfasts with either a low GI (LGI) or a high GI (HGI) in 10 lean healthy controls (group I) and in 9 obese subjects with IGT (group II). The LGI breakfast contained dairy products and fruits while the HGI breakfast was rich in bread. The 2 breakfasts were allocated in a random order and the metabolic and hormonal responses were evaluated both over the post-prandial periods of the breakfast and of the following lunch. Blood glucose concentrations were continuously monitored. Plasma insulin and counter regulatory hormones were measured every 30 min for 360 min. Nutrient oxidation rates were calculated from respiratory exchange data obtained for 60 min in the pre and post-prandial periods. Blood glucose responses and metabolic responses in terms of oxygen consumption and CO2 production were similar in the two groups after a LGI breakfast but became different after the HGI breakfast. In the two groups taken as a whole, changes in CHO oxidation rates observed for 1 hour following the meal, were negatively correlated with the corresponding incremental areas of plasma glucose, this effect being more marked in obese patients with IGT. Such a limitation in CHO oxidation following a HGI CHO load could impair the glycogen cycle and favour fat synthesis. Consequently, breakfasts rich in dairy products and fruits are more recommended in obesity with IGT than breakfasts rich in bread. (C) 1997 Elsevier Science Inc.