Effects of sucrose vs starch diets on in vivo insulin action, thermogenesis, and obesity in rats.

High intake of simple sugars is generally seen as a detrimental factor in the etiology of both obesity and insulin resistance. To examine possible deleterious effects of sucrose, independent of changes in energy intake, rats were fed equal amounts of high-sucrose or high-starch diets over 4 wk. Energy expenditure was assessed by open-circuit respirometry and carcass analysis. In vivo insulin action in individual tissues was assessed with the hyperinsulinemic (1 nmol/L), euglycemic clamp combined with tracer glucose and 2-deoxyglucose administration. Whole-body glucose disposal was impaired by sucrose feeding (clamp glucose infusion rate of 77 +/- 4 vs 124 +/- 6 mumol/[kg.min], p less than 0.001, for sucrose and starch, respectively) because of a major impairment of insulin action at the liver with a smaller contribution from peripheral tissues. Sucrose feeding affected neither basal or stimulated energy expenditure nor accumulation of body fat. In conclusion, sucrose feeding produces a major impairment of insulin action, predominantly because of an effect at the liver.