Association of physical activity and serum insulin concentrations in two populations at high risk for type 2 diabetes but differing by BMI

OBJECTIVE - Physical activity and insulin sensitivity are related in epidem iological studies, but the consistency of this finding among populations th at greatly differ in body size is uncertain. The present multiethnic epidem iological study examined whether physical activity was related to insulin c oncentrations in two populations at high risk for diabetes that greatly dif fer by location, ethnic group, and BMI. RESEARCH DESIGN AND METHODS - The study populations consisted of 2,321 nond iabetic Pima Indian men and women aged 15-59 years from Arizona and 2,716 n ondiabetic men and women aged 35-54 years from Mauritius. Insulin sensitivi ty was estimated by mean insulin concentration (average of the fasting and postload insulin), and total (i.e., leisure and occupational) physical acti vity was assessed by questionnaire. RESULTS - Pima men and women who were more active had significantly (P < 0. 05) lower mean insulin concentrations than those less active (BMI and age-a djusted means were 179 vs. 200 and 237 vs. 268 pmol/l). Similar findings we re noted in Mauritian men and women (94 vs. 122 and 127 vs. 148 pmol/l). In both populations, activity remained significantly associated with mean ins ulin concentration controlled for age, BMI, waist-to-thigh or waist-to-hip ratio, and mean glucose concentrations. CONCLUSIONS - Physical activity was negatively associated with insulin conc entrations both in the Pima Indians, who tend to be overweight, and in Maur itians, who are leaner. These findings suggest a beneficial role of activit y on insulin sensitivity that is separate from any influence of activity on body composition.