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.