Effect of body fat on exercise hemodynamics in sedentary older men

Morbid obesity is often associated with cardiac dilatation and left ventricular dysfunction. The present study investigated whether a similar relationship exists between mild and moderate obesity and left ventricular reserve function in 28 middle aged and older men (58.6 +/- 6.1 years, mean +/- SD). Subjects had a body mass index of 26.4 +/- 2.9 kg/m2, a percent body fat determined by hydrodensitometry ranging from 9.5% to 33.8%, and were carefully screened to exclude cardiovascular disease. Left ventricular function was assessed by gated blood pool scans at rest and during exhaustive upright cycle exercise. There were no significant relationships between resting or exercise cardiac volumes or ejection fraction with percent body fat; however, peak work rate/kg correlated inversely with percent body fat (r = -0.68, p < 0.0001). Heart rate reserve, defined as heart rate at peak work rate minus resting heart rate, declined significantly with increasing percent body fat (r = -0.47, p = 0.01). End diastolic volume index reserve also tended to decline with increasing percent body fat, but stroke volume index and cardiac index reserve were maintained because the decrease in end systolic volume index from rest to maximal exercise was greatest in those subjects with highest percent body fat (r = -0.41, p = 0.03). Therefore, rest and exercise left ventricular function are not related to percent body fat in healthy older men. However, older more obese men have a smaller increase in heart rate and end diastolic volume and a greater decrease in end systolic volume from rest to peak effort as a mechanism to augment exercise cardiac output.