The obesity paradox, cardiorespiratory fitness, and coronary heart disease

Abstract

Objective: To investigate associations of cardiorespiratory fitness (CRF) and different measures of adiposity with cardiovascular disease (CVD) and all-cause mortality in men with known or suspected coronary heart disease (CHD).

Patients and methods: We analyzed data from 9563 men (mean age, 47.4 years) with documented or suspected CHD in the Aerobics Center Longitudinal Study (August 13, 1977, to December 30, 2002) using baseline body mass index (BMI) and CRF (quantified as the duration of a symptom-limited maximal treadmill exercise test). Waist circumference (WC) and percent body fat (BF) were measured using standard procedures.

Results: There were 733 deaths (348 of CVD) during a mean follow-up of 13.4 years. After adjustment for age, examination year, and multiple baseline risk factors, men with low fitness had a higher risk of all-cause mortality in the BMI categories of normal weight (hazard ratio [HR], 1.60; 95% confidence interval [CI], 1.24-2.05), obese class I (HR, 1.38; 95% CI, 1.04-1.82), and obese class II/III (HR, 2.43; 95% CI, 1.55-3.80) but not overweight (HR, 1.09; 95% CI, 0.88-1.36) compared with the normal-weight and high-fitness reference group. We observed a similar pattern for WC and percent BF tertiles and for CVD mortality. Among men with high fitness, there were no significant differences in CVD and all-cause mortality risk across BMI, WC, and percent BF categories.

Conclusion: In men with documented or suspected CHD, CRF greatly modifies the relation of adiposity to mortality. Using adiposity to assess mortality risk in patients with CHD may be misleading unless fitness is considered.

Copyright © 2012 Mayo Foundation for Medical Education and Research. Published by Elsevier Inc. All rights reserved.

Figures

FIGURE 1

Joint effects of cardiorespiratory fitness and body mass index (BMI) (A), waist circumference (WC) (B), and percent body fat (BF) (C), on all-cause mortality. Hazard ratios (boxes) and 95% confidence intervals (error bars represent values) after adjusting for age, baseline examination year, physical activity (active or inactive), smoking (current smoker or not), alcohol intake (>14 drinks/wk or not), hypercholesterolemia, hypertension and diabetes (present or not for each), and family history of cardiovascular disease.

FIGURE 2

Joint effects of cardiorespiratory fitness and body mass index (BMI) (A), waist circumference (WC) (B), and percent body fat (BF) (C), on cardiovascular disease (CVD) mortality. Hazard ratios (boxes) and 95% confidence intervals (error bars represent values) after adjusting for age, baseline examination year, physical activity (active or inactive), smoking (current smoker or not), alcohol intake (>14 drinks/wk or not), hypercholesterolemia, hypertension and diabetes (present or not for each), and family history of CVD. Obese categories (I/II/III) were joined because of the small number of cases.