The coexistence of overweight or obesity and COPD presents both diagnostic and management challenges; however, strategies are available for some patients with these comorbidities to safely lose weight, maintain lean muscle mass and improve exercise tolerance.
- The ‘obesity paradox’ in which mortality appears to be lower in obese patients with COPD than in their normal-weight counterparts is overemphasised in importance.
- The combination of obesity and COPD is associated with decreased exercise tolerance and increased dyspnoea and cardiovascular risk in affected patients.
- Obesity and COPD are two heterogeneous chronic conditions with increasing prevalence.
- There are safe ways for obese patients with COPD to lose weight, maintain lean muscle mass and improve fitness.
- Strategies to encourage healthy lifestyle changes and education on the importance of adequate protein intake can be implemented by GPs in some overweight and obese patients with COPD.
The observation that mortality is lower in obese patients with severe chronic obstructive pulmonary disease (COPD) than in their normal-bodyweight counterparts was first described in a study by Wilson and colleagues in 1989, and gave rise to the theoretical ‘obesity paradox’.1 A larger study by Landbo and colleagues in 1999 demonstrated this association more clearly.2 They showed a relative risk of mortality of 0.3 for patients with severe COPD if they were obese compared with those of normal bodyweight.2 Several other studies have supported this association.3,4
There is, however, considerable doubt about the significance of the above findings and many authors have postulated confounding factors that cause the association.5 These include obesity causing a restrictive defect that leads to an overestimation of severity in this group, and body mass index (BMI) being less predictive of survival than percentage of fat-free mass.6 Interestingly, the paradox is less pronounced in fitter obese patients, and certain patterns of obesity, such as abdominal obesity as measured by increased waist circumference, are associated with lower survival because of myocardial infarction.7,8 It is possible that losing weight has far more impact on mortality, and thus obesity may be less protective than first hypothesised.9
Prevalence of coexisting COPD and overweight or obesity
Although many patients with COPD have malnutrition, a significant proportion are actually overweight or obese.10 A study by Liu and colleagues in 2015 showed that patients who were obese (8.5%) or morbidly obese (15.4%) were more likely to have COPD than patients with normal body weight (6.7%).11
The prevalence of obesity in Australia has increased substantially in recent times from one in 20 adults in 1995 to one in 10 adults in 2011 to 2012.12 A large international study in 2016 in more than 18,000 people found the prevalence of COPD and overweight or obesity ranged from 3 to 47%.13