Adiposity, physical fitness and incident diabetes: the physical activity longitudinal study.

AIMS/HYPOTHESIS: The purpose of this study was to investigate the relationships among adiposity, physical activity, physical fitness and the development of diabetes in a diverse sample of Canadians.
METHODS: The sample included 1,543 adults (709 men and 834 women) from the Canadian Physical Activity Longitudinal Study who were free of diabetes at baseline (1988). Several indicators of adiposity (BMI, waist circumference, WHR, sum of skinfold thicknesses), musculoskeletal fitness (sit-ups, push-ups, grip strength, trunk flexibility), cardiorespiratory fitness (maximal metabolic equivalents [METs]) and leisure-time physical activity levels were measured at baseline. Participants were followed until 2002-2004 for the ascertainment of new cases of diabetes.
RESULTS: The 15.5-year cumulative incidence of diabetes was 5.0% (5.2% in men, 4.9% in women). Adiposity and physical fitness, but not physical activity, were significant predictors of diabetes after adjustment for age, sex and several covariates. For each standard deviation of the indicators of adiposity, the risk of diabetes was 99-194% higher. Conversely, the risk was 70 and 61% lower for each standard deviation of maximal METs and composite musculoskeletal fitness score, respectively. Receiver operating characteristic curve analyses confirmed that neither adiposity nor physical fitness provided a superior prediction of incident diabetes. CONCLUSIONS/
INTERPRETATION: Adiposity and physical fitness were both important predictors of the development of diabetes in this cohort of Canadians.