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Tobacco smoking and oestrogen replacement are associated with lower total and central fat in monozygotic twins
K Samaras1, P J Kelly, T D Spector
1Twin Research Unit, St Thomas' Hospital, London, UK.
Background:
The known postmenopausal increase in cardiovascular risk may relate in part to changes in fat distribution. Environmental factors which are known to influence cardiovascular disease risk may do so in part by influencing body fat and its distribution.
Objectives:
To determine the relationships between tobacco smoking, oestrogen replacement (ERT) and body fat and its distribution in postmenopausal women, independent of genetic factors, physical activity, diet composition and socioeconomic factors.
Design:
Cross-sectional study in normal post menopausal twins.
Subjects:
712 postmenopausal female twins (aged 58.7 +/- 0.2 y, body mass index (BMI) 24.4 +/- 0.1 kg/m2).
Measurements:
Anthropometry; body composition and fat distribution by dual energy x-ray absorptiometry; physical activity, muscle strength, socioeconomic status, dietary composition and dehydroepiandrosterone sulfate (DHEAS).
Results:
In monozygotic pairs discordant for smoking, intrapair differences in total and central fat were greater than that in concordant pairs, with the lower fat mass in the smoking twin. Overall, smokers had a lower weight, BMI, total and central abdominal fat, despite a higher total and saturated dietary fat intake and similar DHEAS levels. The reduction in central fat was not independent of that in total fat. In monozygotic twins discordant for ERT-use the intrapair differences in total and central body fat were significantly greater than in concordant 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 non-users.
Conclusions:
Smoking and ERT-use are associated with lower total and central fat in monozygotic postmenopausal twins. In current smokers, the lower central adiposity appears related to its influence on total body fat. In ERT-users, lower central fat may contribute to the reduced cardiovascular risk associated with postmenopausal oestrogen use.