Obesity is a well-known major risk factor for many disease situations as well as for mortality. This risk is easily identified by a simple measurement of weight or of body mass index (BMI). However, there are several additional related parameters, namely lean body mass, total body fat, visceral fat, body composition and distribution of body fat, which have been investigated in light of their potential prognostic values. A recent study presented data from the Women’s Health Initiative on associations between BMI, body composition, and incident mortality . About 10,500 postmenopausal women, who underwent dual-energy X-ray absorptiometry scans (DXA) for estimation of total body fat and lean body mass, were followed for 13.6 (± 4.6) years. Their baseline characteristics were: age 63 (± 7) years; age at menopause 47 (± 7) years; weight 74 kg (± 16) kg; BMI 28 (± 6) kg/m2; total lean body mass 53% (± 7%); total fat body mass 44% (± 7%). Overall, BMI 35 kg/m2 was associated with increased mortality (adjusted HR 1.45, 95% CI 1.16–1.82), while total body fat and lean body fat were not. Among women aged 50–59 years, higher % total body fat increased risk of death (HR 2.44, 95% CI 1.38–4.34) and higher % lean body mass decreased risk of death (HR 0.41, 95% CI 0.23–0.74), despite broad-ranging BMIs. However, the relationships were reversed among women aged 70–79 years (p < 0.05). When the results were stratified by waist circumference, the protective association of higher lean body mass in younger women (age < 60 years) was seen only among those with low waist circumference (< 88 cm) and not those with larger waists (≥ 88 cm). Furthermore, the increased mortality risk among older women (ages 60–69 and ≥ 70 years) with higher lean body mass was seen only among those with a high waist circumference.
Sackler School of Medicine, Tel-Aviv University, Tel-Aviv, Israel
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