Abstract P144: Determinants of Cardiorespiratory Fitness in an Overweight and Obese High-Risk African-American Population
Introduction: African Americans (AA) often have low levels of cardiorespiratory fitness, explained in prior studies primarily by body mass index (BMI). Given the marked heterogeneity in the ratio of metabolically active lean (muscle) mass versus fat mass, even across ranges of higher BMI, we examined the extent to which higher levels of lean versus fat mass are independently associated with fitness in healthy overweight and obese AA from families with early-onset coronary disease.
Methods: Subjects were screened for demographics, smoking, blood pressure, levels of blood lipids, hsCRP, glucose, and insulin; body composition was determined by dual energy X-ray absorptiometry; the ratio of lean mass to fat mass was calculated and log-transformed for analysis. Habitual physical activity was assessed with the Stanford 7-Day Physical Activity Recall. Fitness was expressed as VO2peak attained during maximal treadmill testing. Linear regression was used to model VO2peak, adjusted for cardiovascular risk factors and nonindependence of families.
Results: Participants (n=195; 69% women) were 44.8 ± 11 years old with mean BMI 34 ± 5 kg/m2. In regression analysis, increased lean to fat mass ratio was associated with increased VO2peak (p< 0.0001), independent of age, sex, BMI and other important variables (Table). Lean to fat mass ratio explained more than 46% of the variance in VO2peak, while age, sex, BMI, smoking, and triglycerides together accounted for <10% of the variance in VO2peak.
Conclusions: The ratio of lean to fat mass was the key determinant of cardiorespiratory fitness, independent of sex, age, and the magnitude of obesity in this cohort of high-risk overweight and obese AAs. The results suggest that interventions that preserve or increase lean mass may increase cardiorespiratory fitness.
- © 2013 by American Heart Association, Inc.