BackgroundHelper type 1 T cell polarization and monocyte cell activation influence forced expiratory volume in 1 second/forced vital capacity and are affected by body mass index (BMI), insulin resistance, and serum lipoproteins. No study has assessed the impact of metabolic syndrome components on asthma symptom control. ObjectiveTo determine the prevalence of patients with metabolically unhealthy obesity (MUO) and asthma. Our secondary objective was to compare the strength of associations among asthma outcomes in patients with obesity measured by BMI, waist circumference, and MUO. MethodsA cross-sectional analysis of the combined 2011 to 2016 cycles of the National Health and Nutrition Examination Survey was performed among persons with asthma. Metabolically unhealthy obesity was defined as a BMI of at least 30 kg/m2 and one of the following: increased waist circumference, insulin resistance, low physical activity, hyperlipidemia, or hypertension. Multiple logistic regression models were computed to assess asthma exacerbations and emergency department use for asthma in patients with MUO compared with unhealthy obesity. ResultsAmong respondents with MUO, 50.09% (n = 543; N = 17,011,880) had asthma compared with 7.91% in those with metabolically healthy obesity (n = 77; N = 2,685,858). Persons with MUO were significantly more likely to report the use of an emergency department for their asthma symptoms within the past 12 months (odds ratio, 3.53; 95% confidence interval, 1.54-8.09; P < .05). Persons with elevated waist circumference were more likely to report asthma exacerbations (odds ratio, 1.58; 95% confidence interval, 1.09-2.26). No significant difference existed in reported asthma exacerbations or emergency department use in patients measured by BMI. ConclusionMUO is associated with increased emergency department use for asthma and is better at predicting exacerbations and emergency department use than BMI alone.