Effect of weight loss on whole body and cellular lipid metabolism in severely obese humans.

We evaluated the effect of diet-induced weight loss on whole body and cellular lipid metabolism in persons with severe upper body obesity in two study protocols. In protocol 1, palmitate and glycerol rates of appearance (Ra) in plasma were determined during basal conditions in seven subjects [initial body mass index (BMI) = 41.3 +/- 2.2 kg/m2] before and after 20.4 +/- 3.0 kg weight loss. Total glycerol and palmitate Ra decreased from 231.0 +/- 19.4 and 166.2 +/- 16.6 mumol/min, respectively, before weight loss to 162.7 +/- 9.5 and 105.0 +/- 9.7 mumol/min, respectively, after weight loss (P < 0.01). However, glycerol and palmitate Ra expressed per kilogram fat mass were similar both before and after weight loss. In protocol 2, subcutaneous abdominal adipose tissue was obtained before and after 14.4 +/- 2.1 kg weight loss in five subjects (initial BMI = 41.6 +/- 2.6 kg/m2). Weight loss caused a 38 +/- 8% decrease in adipocyte hormone-sensitive lipase concentration (P < 0.05) but was not associated with any consistent changes in the concentrations of GTP-dependent regulatory proteins, Gi1 alpha, Gi2 alpha, and G3 alpha. We conclude that diet-induced weight loss ameliorates the increase in basal lipolytic rates in persons with severe upper body obesity. These alterations are associated with changes in cellular hormone-sensitive lipase but not GTP-dependent regulatory protein concentrations.