DIETARY STARCH COMPOSITION AND LEVEL OF ENERGY-INTAKE ALTER NUTRIENT OXIDATION IN CARBOHYDRATE-SENSITIVE MEN

The effect of dietary starch type on components of 24-h energy expendi ture (total, sleep, exercise) were examined in 13 hyperinsulinemic and nine control men, aged 28-58 y. Subjects consumed products containing 70% amylopectin or 70% amylose cornstarch for two 14-wk periods in a crossover design. A 10-wk period of starch replacement in the subjects ' self-selected diets was followed by a 4-wk controlled feeding period at 100% maintenance energy in-take; diets during the last 4 d of the controlled feeding period provided excess energy, i.e., 125% of mainte nance energy. Data for insulin, glucose, 24-h energy expenditure and i ts components, respiratory quotient and nutrient oxidation were analyz ed by ANOVA for mixed models. Although insulin and glucose responses t o a starch tolerance test remained greater for hyperinsulinemic than f or control subjects, both were reduced with high amylose consumption ( P < 0.04). No component of energy expenditure was significantly affect ed by dietary starch or subject type. However, excess energy intake di d increase metabolic energy expenditure (P < 0.0001). Protein oxidatio n increased with excess energy intake when subjects consumed the high amylopectin starch but did not increase in response to excess energy c onsumption when the high amylose diet was consumed, suggesting increas ed protein retention. The magnitude of the response in carbohydrate an d fat oxidation was blunted in hyperinsulinemic subjects consuming exc ess levels of the amylose diet. This may be due to an improvement in o verall insulin response or to a change in available substrates for oxi dation resulting from microbial fermentation.