Relationship between body mass index and percent body fat in aging females.

Background: The purpose of this study was to compare the relationship between body fat percent utilizing Bod Pod (BF%) and body mass index (BMI) in premenopausal, perimenopausal, and postmenopausal women between the ages of 18-71 years. Methods: BF%, BMI, bioelectrical impedance, waist-to-hip, waist circumference, and activity level were assessed for a total of 252 female participants (106 premenopausal, 64 perimenopausal, and 82 postmenopausal women). BMI cut-points used to characterize overweight and obese were 25 kg/m2 and 30 kg/m2, respectively and 30% and 35%, respectively to define overweight and obesity by BF%. Using BF%, receiver operator characteristic (ROC) curves established optimal BMI cut-points. Physical activity levels were scored as inactive, minimally active, or active. Results: BF% significantly increased (P<0.05) from premenopausal (35.10±8.35%) to perimenopausal (39.20±8.62%) to postmenopausal (43.49±8.51%) although there was no significant change in BMI from premenopausal (25.73±5.86 kg/m2) to perimenopausal (26.32±6.41 kg/m2) to postmenopausal (27.61±6.10 kg/m2). For overweight (BF% ⩾ 30) using BMI ⩾ 25 kg/m2 and obese (BF% ⩾ 35) using BMI ⩾ 30 kg/m2 the best sensitivity and specificity was seen when cut-points were reduced to 23 kg/m2 for overweight and 24 kg/m2 for obesity. Premenopausal women were significantly (P < 0.05) less fat than perimenopausal and postmenopausal women. Perimenopausal women were also significantly (P < 0.05) less fat than postmenopausal women. Participants who were inactive were significantly (P < 0.05) fatter than participants who were minimally active and active. Conclusion: Although females are not gaining significant weight in their lifetime, they increase body fat from premenopausal to postmenopausal. [ABSTRACT FROM AUTHOR]