Resting energy expenditure (REE) is often elevated in patients with chronic obstructive pulmonary disease (COPD), but no data are available regarding total energy expenditure in free living conditions. We compared total daily energy expenditure (TDE) in eight COPD patients (FEV1 36 +/- 13%) admitted to a pulmonary rehabilitation center and eight independently living healthy subjects, matched for sex, age, and body mass index (BMI). TDE was measured over a 2-wk interval using doubly labeled water in combination with measurement of REE and body composition. The COPD patients had a significantly higher TDE than the healthy subjects (2,499 +/- 320 kcal/d and 2,107 +/- 88 kcal/d, respectively, p < 0.01). The nonresting component of TDE (TDE-REE: physical activity and diet-induced thermogenesis [DIT]) was significantly higher in the COPD patients than in the healthy subjects, resulting in a ratio between TDE and REE of 1.7 +/- 0.2 and 1.4 +/- 0.1, respectively (p < 0.01). The results indicate that COPD patients exhibit an increased TDE in comparison with healthy subjects. The difference could by attributed to an increase in the nonresting component of TDE, since REE was comparable between the groups.