In Vitro Lipolysis is Associated with Whole-Body Lipid Oxidation and Weight Gain in Humans

Objective: To assess the association of adipocyte size with cellular lipolysis and between cellular lipolysis and whole-body lipid oxidation. This study also assessed the association between adipocyte size and cellular lipolysis with weight and fat mass gain. Methods: Subjects had assessment of percent body fat (% fat) and adipose tissue biopsy for in vitro lipolysis (n = 325), and a subset of subjects had measurement of whole-body lipid oxidation (n = 112). A subset of subjects (n = 243) returned for repeated measurements of body weight and composition (mean follow-up 8.2 +/- 5.5 years). Results: In vitro lipolysis (r = 0.47, P < 0.0001) and adipocyte size (r = 0.49, P < 0.0001) were strongly associated with % fat. In vitro lipolysis (P = 0.04) but not adipocyte size (P = 0.44) was associated with whole-body fat oxidation. Adipocyte size was not associated with rate of percent weight gain (P = 0.20) but was negatively associated with rate of percent fat mass gain (P = 0.01). In vitro lipolysis was negatively associated with rate of percent weight gain (P = 0.02) and had a marginal negative association with rate of percent fat mass gain (P = 0.08). Conclusions: These results indicate inherent characteristics of adipocytes, including size and lipolytic activity, may be important determinants of whole-body lipid oxidation and subsequent weight gain.