TOBACCO SMOKING AND ESTROGEN REPLACEMENT ARE ASSOCIATED WITH LOWER TOTAL AND CENTRAL FAT IN MONOZYGOTIC TWINS

BACKGROUND: The known postmenopausal increase in cardiovascular risk m ay relate in part to changes in fat distribution. Environmental factor s which are known to influence cardiovascular disease risk may do so i n part by influencing body fat and its distribution. OBJECTIVES: To de termine the relationships between tobacco smoking, oestrogen replaceme nt (ERT) and body fat and its distribution in postmenopausal women, in dependent of genetic factors, physical activity, diet composition and socioeconomic factors. DESIGN: Cross-sectional study in normal post me nopausal twins. SUBJECTS: 712 postmenopausal female twins (aged 58.7 /- 0.2 y, body mass index (BMI) 24.4 +/- 0.1 kg/m(2)). MEASUREMENTS: A nthropometry; body composition and fat distribution by dual energy x-r ay absorptiometry; physical activity, muscle strength, socioeconomic s tatus, dietary composition and dehydroepiandrosterone sulfate (DHEAS). RESULTS: In monozygotic pairs discordant for smoking, intrapair diffe rences in total and central fat were greater than that in concordant p airs, with the lower fat mass in the smoking twin. Overall, smokers ha d a lower weight, BMI, total and central abdominal fat, despite a high er total and saturated dietary fat intake and similar DHEAS levels. Th e reduction in central fat was not independent of that in total fat. I n monozygotic twins discordant for ERT-use the intrapair differences i n total and central body fat were significantly greater than in concor dant pairs, with the lower fat measure in the ERT-using twin. Overall, current ERT-users had similar body weight, BMI and total fat compared to non-users but had lower central fat. There were no differences in activity levels, diet or socioeconomic factors between ERT-users and n on-users. CONCLUSIONS: Smoking and ERT-use are associated with lower t otal and central fat in monozygotic postmenopausal twins. In current s mokers, the lower central adiposity appears related to its influence o n total body fat. In ERT-users, lower central fat may contribute to th e reduced cardiovascular risk associated with postmenopausal oestrogen use.