OBJECTIVE To examine resting metabolic rate in patients with congestive heart failure as a cause of cardiac cachexia and associated weight loss. METHODS Cross-sectional study. METHODS Baltimore Veterans Affairs Medical Center. METHODS 20 men with heart failure (mean age +/- SD, 69 +/- 7 years) and reduced ejection fraction (mean, 0.24 +/- 0.10) and 40 healthy men (mean age, 69 +/- 7 years). RESULTS Patients with heart failure had smaller fat-free mass than did controls (53 +/- 8 kg compared with 56 +/- 6 kg; P < 0.09), but no difference in fat mass existed (21 +/- 8 kg compared with 19 +/- 8 kg). Measured resting metabolic rate was 18% higher in patients with heart failure than in controls (1828 +/- 275 kcal/d compared with 1543 +/- 219 kcal/d; P < 0.01); no difference in caloric intake existed (2144 +/- 479 kcal/d compared with 2174 +/- 826 kcal/d). The difference in resting metabolic rate between the two groups was even more striking when indexed per kilogram of fat-free mass. CONCLUSIONS Higher resting metabolic rate in patients with heart failure at least partially accounts for otherwise unexplained weight loss. Present caloric guidelines, which were established in healthy elderly persons, substantially underestimate the resting caloric needs of elderly persons with heart failure.