Body mass index

• The normal range for BMI is 20–25 • A low BMI (<20) is a poor prognostic feature in respiratory patients and increases the risk of death in COPD • Patients with a low BMI have an increased risk of lean muscle mass loss • This leads to peripheral muscle weakness and makes exercising more difficult • Breathlessness can make eating difficult. • Practical advice, such as eating small, frequent high-calorie meals can help reverse the weight loss • Patients with a low BMI who do not respond to simple advice should be referred for dietetic advice and be encouraged to exercise • Patients with a high BMI are likely to have greater impairment of activity and more breathlessness than patients with a normal BMI • This in turn can lead to the patient having even less exercise and a worsening quality of life • Patients should be given advice on how to lose weight