ObjectiveTo explore the relationship of obesity with asthma control and airway inflammatory phenotype. MethodsA cross-sectional prospective study was conducted on 101 patients with asthma. Asthma control level was assessed by Asthma Control Test (ACT) and GINA. Furthermore, height and weight were measured and body mass index (BMI) was calculated. Lung function and sputum induction were performed, and differential cell count was obtained from induced sputum and peripheral blood. ResultsNinety eligible patients were divided into 3 groups as a normal-weight group (n=54), an over-weight group (n=21) and an obesity group (n=15). The asthma control levels were different among three groups (P=0.019 for ACT and P=0.014 for GINA, respectively). BMI was positively related to the number of neutrophils in induced sputum (r=0.29, P=0.039). Increased BMI deteriorated asthma control levels assessed by ACT[OR=1.84, 95% CI (1.04, 3.23), P=0.035] and GINA[OR=2.27, 95% CI (1.27, 4.07), P=0.006] in a dose-response manner. Obesity indicated poor asthma control assessed by ACT (P=0.015) and GINA (P=0.008) after adjusting for age, sex, duration of asthma, FEV1%pred, smoking, and the number of neutrophils in peripheral blood. ConclusionsIn Chinese individuals with asthma, neutrophilic inflammatory phenotype dominates the airway inflammation of obesity-associated asthma. Obesity is a risk factor that deteriorates asthma control level in a significant dose-response manner.