Predictors of Postmenopausal Body Mass Index and Waist Hip Ratio in the Oklahoma Postmenopausal Health Disparities Study

Objective: The goal of the current study has been to examine systematically the respective roles of nutrition, exercise, menopausal weight gain, moderate drinking and smoking as determinants of body mass index (BMI) and waist hip ratio (WHR) in a setting in which the role of race or ethnic group could be simultaneously or individually evaluated as predictors of BMI and WHR. Because the use of estrogen replacement has been reported to affect estimates of body fat mass in postmenopausal women, endocrine factors have also been evaluated. Methods: The design is cross-sectional with historical prospective elements. The study has a biomedical focus and is not an epidemiologic study. Data are from 649 women recruited into The Postmenopausal Health Disparities Study in Oklahoma. The study population was composed of 649 postmenopausal women: American Indian: 226 (34.9%), Asian: 21 (3.2%), Black: 78 (12.0%), Hispanics: 54 (8.3%) and Whites: 270 (41.6%). Recruitment occurred between 1994 and late 1999 in Oklahoma. Results: In this multi-racial, multi-ethnic study population, there was statistical heterogeneity in all nutrition/dietary and exercise variables as well as in other potential determinants of BMI and WHR. In contrast to the literature available for postmenopausal women in which postmenopausal status, estrogen replacement and race have rarely been taken into account, the results of multi-linear regression revealed the following: Significant predictors for BMI, with or without WHR specified, included the neuroendocrine factors, menopausal weight gain, smoking, mean fitness (i.e., difficulty performing physical activities), fat as percent of total calories, moderate drinking and being Asian or Black. When WHR was not included, total calories and socioeconomic status also entered the model. The statistical predictors of WHR in the total study population with BMI in the equation included BMI and the neuroendocrine variables of FSH, E2, but not ERT, as well as the interaction of higher intensity exercise fitness with frequency, socioeconomic status and being American Indian or Asian. When BMI was not included in the model, in addition to the neuroendocrine factors, the interaction of lower intensity exercise fitness with frequency, fat as percent of total calories, age living alone and being American Indian or and Black were significant predictors of WHR. The predictors of both BMI and WHR were found to differ among individual racial and ethnic groups. Conclusions: Given the role of increased body fat and obesity in disease risk and the substantial differences in life expectancy among the racial and ethnic groups, the findings of this study, particularly in contrast to literature reports, strongly suggest that a whole variety of factors including hormonal status and race need to be considered when examining the role of dietary factors and physical activity in relation to estimates of body fat mass and disease risk.