Carbohydrate-induced thermogenesis in obese women. Effect of insulin and catecholamines

Results of studies on diet-induced thermogenesis in obese persons are contr adictory. A number of factors have been postulated to mediate the obligator y and facultative component of thermogenesis. This study was designed to in vestigate some further factors mediating the carbohydrate-induced thermogen esis in obese women. In 13 obese women, thermogenic responses to glucose an d fructose were compared and related to subsequent hormonal changes. The th ermogenic effect after fructose ingestion was significantly (p<0.006) highe r in comparison with glucose, despite tower values for both glucose and ins ulin concentrations. Carbohydrate oxidation was significantly higher after fructose (81+/-7 E% vs 62+/-10 E% p<0.01) while oxidation of fat was lower (10+/-9 E% vs 21+/-12 E% p<0.01). These effects may partly be due to the de novo lipogenesis and/or to changes in cellular metabolism. No clear relati onship could be found between thermogenesis and the activity of the sympath etic nervous system, as expressed by urinary catecholamine levels. These re sults indicate that not insulin but the cellular rate of carbohydrate metab olism is responsible for the thermogenic response to different carbo-nutrie nts. (C) 1999, Editrice Kurtis.