Basal metabolic rate and its determinants in postmenopausal women

The basal metabolic rate (BMR) of 70 postmenopausal women (age: 60.6 ± 4.2 yrs., height: 154.9 ± 5.2cm, body weight (BW): 52.7 ± 6.2 kg; mean ± SD) was evaluated in relation to body composition (body fat mass (FM): 17.3 ± 3.9 kg, lean body mass (LBM): 35.3 ± 3.6 kg). BMR was 1,148 ± 126 kcal/day, 21.9 ± 2.2 kcal/kgBW/day, 32.7 ± 3.2 kcal/kgLBM/day in all subjects. BMR (kcal/day) significantly correlated with BW (r = .635, p < 0.001) and LBM (r = .598, p < 0.001). When divided into two groups, (lower %fat group (LF: < 35%fat) and higher %fat group (HF ; ≥ 35%fat)), BW and FM were significantly higher in HF than in LF (BW: 56.6 ± 6.4 vs 51.0 ± 5.3 kg, FM: 21.7 ± 2.8 vs 15.5 ± 2.7 kg, p < 0.001, respectively). No difference was observed in LBM between the two groups (34.9 ± 3.9 vs 35.5 ± 3.5 kg). BMR (kcal/kgBW/day) was lower in HF than in LF (21.0 ± 1.8 vs 22.3 ± 2.3, p < 0.05), but HF group had higher BMR in terms of kcal/kgLBM/ day than LF (34.0 ± 3.1 vs 32.1 ± 3.1. p < 0.05). Multiple regression analysis was performed to predict BMR. A single predictor LBM and a pair of predictors LBM and FM explained 35.7% and 42.7% of the variance of BMR. This study suggested that a decrease in LBM is a major factor in affecting the reduction of BMR in postmenopausal women, whereas FM gained after menopause could be considered to have metabolic activity related to BMR.