In order to assess the influences of obesity and diabetes on the regulation of fat mobilization, plasma FFA and glycerol concentration before and during oral glucose tolerance tests were correlated with weight and glucose tolerance in forty-nine obese and nonobese nondiabetic and nonketotic mildly diabetic males.
Basal FFA and glycerol levels were directly related to the degree of carbohydrate intolerance only in the obese and correlated with weight in the diabetic subjects only. Thus, elevated basal FFA and glycerol, presumably indices of increased basal lipolysis, were found only in diabetic subjects who were also obese. Neither uncomplicated obesity nor nonketotic diabetes in the nonobese was found to be characterized by elevated basal FFA and glycerol levels.
After glutose ingestion glycerol concentrations fell at similar rates in both nondiabetic and diabetic groups, which indicated that lipolysis ceased normally in nonketotic diabetes. A delayed decline in FFA was observed in obese diabetics only, evidence consistent with impaired re-esterification in this group. These findings suggest that abnormalities in regulation of fat mobilization may become manifest in nonketotic diabetes only in the presence of obesity.