OBJECTIVE: To investigate the effects of short term (15 days) cafeteria diet feeding on the expression of b b 3 -AR in vivo and its association with lipolytic stimulation induced by b b 3 -AR agonist CGP12177A in isolated white adipocytes. ANIMALS: Six female and 6 male Wistar rats (at 4 weeks of age) were fed on a cafeteria diet plus standard diet for 15 days. The remaining 12 age-and sex-matched rats always received standard diet only. MEASUREMENTS: White gonadal adipose tissue was isolated and used for the determination of b b 3 -AR and leptin expression, and for in vitro studies of lipolytic activity. RESULTS: Control male rats had higher levels of both b b 3 -AR and leptin mRNA in white adipose tissue than their female counterparts. Both male and female rats up-regulated the levels of both b b 3 -AR and leptin mRNA in response to 15 day cafeteria diet feeding. Noradrenaline-and isoprenaline-induced lipolysis were signi®cantly increased in fat cells from control females compared to their male counterparts. CGP12177A stimulation resulted in signi®cantly higher glycerol release in fat cells from cafeteria diet-fed female rats, whereas there were no differences due to dietary treatment in male rats. The maximal lipolytic response of forskolin (stimulating adenylyl cyclase) and dibutyryl cyclic AMP (cyclic AMP analogous) was not affected by sex or cafeteria diet feeding. CONCLUSION: Cafeteria diet feeding brings about higher excess body weight and impaired adipose tissue lipolytic activity in female rats compared to male rats. Thus, the higher levels of b b 3 -AR mRNA induced by cafeteria feeding are not indicative per se of an increase of the lipolytic response of the adipocytes. The changes seen in other adrenoceptor subtypes (b b 1 and b b 2 ) may be more determinant of the overall lipolytic response of adipocytes.