Adipose tissue lipolysis after long-term overfeeding in identical twins.

Ten pairs of young male sedentary, non-obese, monozygotic (MZ) twins, aged 21 +/- 2 years (mean +/- s.d.), were overfed for a period of 100 days during which they ingested 4.2 MJ (1000 kcal) per day above their individual energy needs, 6 days per week. There was a mean 8.4 kg increase in body weight and the average gain in body fat reaches 5.6 kg (P less than 0.0001). A biopsy of subcutaneous abdominal fat was performed, before and after the treatment, to determine fat cell weight as well as basal and catecholamine stimulated lipolyses from collagenase isolated adipocytes. Although analysis of variance revealed an increase in abdominal fat cell weight, no significant changes were noted in basal and catecholamine-stimulated lipolyses, due to large variation among individuals, results being expressed either per cell number or corrected for cell surface area. However, significant intrapair resemblance was observed in the changes of basal and epinephrine stimulated lipolyses (ri of about 0.60 in both cases), suggesting a concordant within-pair response, despite large between-pair variation. These results support the notion that the genotype may play an important role in regulating the response of abdominal adipose cells lipolytic activity to caloric excess.