Suppression of norepinephrine-induced thermogenesis in human obesity by diet and weight loss

The response of metabolic rate to norepinephrine infusion was studied in seven obese subjects before and after large amounts of weight loss. Resting metabolic rate fell from a mean of 2254 kcal (9.4 MJ) to 1682 kcal (7.0 MJ) per 24 h. The thermic response to norepinephrine infusion was reduced by 50 percent from 7527 (31.5 MJ) to 3369 (14.0 MJ) kcal/24 h/T0-45 following weight loss and on continued diet. This adaptation to weight loss could contribute to the diminished rate of weight loss that occurs with continued dieting. Previous contradictory findings of normal and reduced norepinephrine-induced thermogenesis in human obesity could result from subjects being studied under different dietary conditions.