Waist circumference vs body mass index in association with cardiorespiratory fitness in healthy men and women: a cross sectional analysis of 403 subjects

Abstract

Objective: Body mass index (BMI) is more commonly used than waist circumference as a measure of adiposity in clinical and research settings. The purpose of this study was to compare the associations of BMI and waist circumference with cardiorespiratory fitness.

Methods: In a cross-sectional study of 403 healthy men and women aged 50 ± 8.8 years, BMI and waist circumference were measured. Cardiorespiratory fitness was assessed from estimated maximal O2 uptake (VO2max), as calculated from a maximal fitness test.

Results: Mean BMI (kg/m2) was 27.8 ± 3.7 and 25.5 ± 4.6; and mean waist circumference (cm) 94.1 ± 9.7 and 84.3 ± 10.4 for men and women, respectively. Both men and women reported an average of 2.5 hours of weekly sports related physical activity, and 18% were current smokers. Correlation coefficients between both BMI and waist circumference, and VO2max were statistically significant in men (r= -0.280 and r= -0.377, respectively, p>0.05 for both) and in women (r= -0.514 and r= -0.491, respectively, p>0.05 for both). In women, the contribution of BMI to the level of VO2max in a regression model was greater, while in men waist circumference contributed more to the final model. In these models, age, hours of training per week, and weekly caloric expenditure in sport activity, significantly associated with VO2max, while smoking did not.

Conclusion: The differences observed between the sexes in the associations of BMI and waist circumference with VO2max support the clinical use of both obesity measures for assessment of cardiorespiratory fitness.

Figure 1

The interaction between obesity indexes (BMI and waist circumference) and cardiorespiratory fitness, as measured by calculated VO₂max. A: The interaction between BMI and VO₂max in men and women. For the for interaction between BMI*sex and VO₂max in the adjusted multivariate linear regression models P = 0.057. Abbreviation: BMI = Body Mass Index. R² - a measure of goodness-of-fit in linear regression. B: The interaction between waist circumference and VO₂max in men and women. For the interaction between WC*sex and VO₂max in the adjusted multivariate linear regression models P = 0.063. Abbreviation: WC = waist circumference. R² - a measure of goodness-of-fit in linear regression.