Metabolic effects of continuous feeding.

To study the metabolic effects of slowing absorption, as a possible mechanism for the blood glucose and lipid-lowering effects of soluble fiber and low glycemic index (GI) foods, seven healthy men consumed a liquid formula diet either as three equal meals at 4-hour intervals, or by continuously sipping the same amount of formula over the 12-hour study period. Meal-related fluctuations of blood glucose, insulin, and triglycerides were seen during three meals, but not during sipping. Mean 12-hour levels of blood glucose and beta-hydroxybutyrate (beta OHB) were equivalent on sipping and three meals. The total integrated insulin area was reduced by 32% on sipping (P less than .01), but this was not explained by the 16% (NS) reduction in serum C-peptide response. Mean serum free fatty acid (FFA) and cholesterol levels were reduced by 20% and 2.6%, respectively (P less than .01). It is concluded that the reduced glycemic responses seen after soluble fiber-enriched meals and low GI foods can be explained by slow absorption. Although the overall mean daily blood glucose levels may not be reduced by slowing carbohydrate absorption in nondiabetic subjects, this is achieved at considerably lower ambient serum insulin concentrations. The reduction of insulin levels may be an important mechanism for the serum cholesterol-lowering effect of soluble fiber and low GI foods.