The interactions between obesity and chronic obstructive pulmonary disease (COPD) are being increasingly explored. In part, this is due to the globally increasing prevalence rates of obesity. The prevalence of obesity in COPD patients is variable, and it seems that obesity is more common in COPD patients compared with subjects who do not have COPD. However, further studies are encouraged in this area due to observed inconsistencies in the current data. In this review, we focus on the knowledge of the effects of obesity on dyspnea, pulmonary function, exercise capacity and exacerbation risk. Reduction of dyspnea is one of the main therapy targets in COPD care. There is still no consensus as to whether obesity has a negative or even a positive effect on dyspnea in COPD patients. It is hypothesized that obese COPD patients might benefit from favourable respiratory mechanics (less lung hyperinflation). However, despite less hyperinflation, obesity seems to have a negative influence on exercise capacity measured with weight-bearing tests. This negative influence is not seen with weight-supported exercise such as cycling. With respect to severe exacerbations, obesity seems to be associated with better survival. In summary, it is concluded that due to differences in study methodology and cohort selection, there are still too many knowledge gaps to develop guidelines for clinical practice. Further exploration is needed to get conclusive answers.

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Objectives Our aim was to study the associations between resting lung hyperinflation, weight-bearing exercise-induced dyspnea and adipose distribution in obese and normal-weight COPD patients. Methods We performed a comparison between 80 obese COPD patients (COPDOB) with 80 age- and FEV1 matched normal-weight COPD patients (COPDNW). Dyspnea was assessed by the mMRC scale and the Borg dyspnea score before and after a 6 min walk test. Further characterization included spirometry, body plethysmography and metronome paced tachypnea (MPT) to estimate dynamic hyperinflation. Body composition was assessed with bioelectrical impedance analysis. Associations between dyspnea scores and BMI and body composition groups were studied using logistic regression models. Results COPDOB patients had attenuated increases in TLC, FRC and RV compared to COPDNW patients ( p < 0.01). The groups had comparable 6 min walking distance and ΔFRC upon MPT ( p > 0.05). Compared to COPDNW, COPDOB patients reported more often a mMRC ≥ 2 (65 vs 46%; p = 0.02; OR 3.0, 95% CI 1.4–6.2, p < 0.01) and had higher ΔBorg upon 6MWT: 2.0 (SEM 0.20) vs. 1.4 (SEM 0.16), p = 0.01; OR for ΔBorg ≥ 2: 2.4, 95% CI 1.1–5.2, p = 0.03. Additional logistic regression analyses on the associations between body composition and dyspnea indicated that increased body fat percentage, fat mass index and waist-to-hip ratio were associated with higher ORs for mMRC ≥ 2 and ΔBorg upon 6MWT ≥ 2. Conclusion Despite its beneficial effect on resting lung hyperinflation, adiposity is associated with increased weight-bearing exercise-induced dyspnea in COPD.

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