Physical Activity, Physical Fitness And Body Mass Index As Predictors Of Future Obesity In Canada

Abstract

Obesity is a growing population health issue in Canada and the identification of the determinants of obesity is important for the development of prevention strategies. PURPOSE To determine the relationships between physical activity, physical fitness, body mass index (BMI) and the development of obesity. METHODS The sample consisted of 472 adults (18+ y; 230 men and 242 women) from the Canadian Physical Activity Longitudinal Study (PALS; 2002–04). The PALS cohort is a longitudinal follow-up of participants from the 1981 Canadian Fitness Survey and 1988 Campbell's Survey of Well-Being. Data on self-reported physical activity, smoking status, alcohol consumption and measured height, weight and maximal oxygen consumption (VO2max, estimated from sub-maximal step-test) were collected in 1981 and 1988. The mean BMI (kg/m2), physical activity levels, and VO2max were calculated across the 1981 and 1988 measures. Self-reported height and weight were collected in the 2002–04 survey, and participants were classified as obese if their BMI was ≥30 kg/m2. Logistic regression was used to predict obesity in 2002–04 from age, smoking status and alcohol consumption at baseline (1981), and average BMI, physical activity and VO2max between 1981–1988. RESULTS Higher average VO2max in 1981–88 was associated with lower odds of obesity (OR=0.87; 95% C.I.: 0.76–0.99, p<0.05), while higher average BMI in 1981–88 was associated with higher odds of obesity (OR=1.83; C.I.: 1.52–2.20, p<0.0001) in 2002–04. Further, higher baseline age was associated with lower odds of obesity in 2002–04 (OR=0.89; 95% C.I.: 0.83–0.95, p<0.001). In contrast, mean physical activity (OR=1.04; C.I.: 0.82–1.32) was not a significant predictor of the development of obesity. CONCLUSIONS The results indicate that measured physical fitness and BMI are important predictors of future obesity. Higher levels of physical fitness are associated with a lower risk of future obesity, independent of BMI. On the other hand, higher BMI was associated with a greater risk of obesity, which highlights the stability of adiposity over time. Strategies to identify individuals at an increased risk of developing obesity should include measurements of BMI and physical fitness.