Although underweight has been the traditional nutritional concern in patients with COPD, overweight and obesity are becoming important issues in this disease. In a rehabilitation study, investigators found that 66% of patients with moderate to severe COPD were either overweight or obese according to the WHO obesity classification (BMI ≥ 25 kg/m2). Obesity and COPD being two frequent conditions, it is important to understand the nature of their interactions.