Adipose tissue cellularity, in vitro glycerol release, and in vivo glucose metabolism were examined in ten markedly obese subjects, ages thirteen to fifty-four, before and after weight reduction.
Prior to reduction adipose cells were larger and exhibited higher rates of lipolysis than smaller postreduction cells. Incubations containing epinephrine, epinephrine plus insulin and insulin alone also revealed significant decreases in absolute rates of glycerol release in the postreduction state. However, when the data were expressed as per cent change, in vitro hormonal activity did not appear to be influenced by changes in cell size. Weight reduction was also accompanied by improvement in oral glucose tolerance tests, lower fasting levels of plasma free fatty acids and decreased values of circulating immunoreactive insulin, fasting and following oral glucose. Studies of adipose cell number revealed that obese adolescents display hypercellularity comparable to that observed in obese adults. As in the adult, weight loss resulted in improved glucose tolerance and a decrease in adipose cell size without a significant change in total adipose cell number.
Thus decreased rates of lipolysis of smaller adipocytes were associated with the improved lipid and glucose metabolism found in obese subjects after weight reduction.