Behavioral weight loss and physical activity intervention in obese adults with asthma. A randomized trial

Abstract

Rationale: The effect of weight loss on asthma in obese adults warrants rigorous investigation.

Objectives: To examine an evidence-based, practical, and comprehensive lifestyle intervention targeting modest weight loss and increased physical activity for asthma control.

Methods: The trial randomized 330 obese adults with uncontrolled asthma to receive usual care enhanced with a pedometer, a weight scale, information about existing weight management services at the participating clinics, and an asthma education DVD, or with these tools plus the 12-month intervention.

Measurements and main results: The primary outcome was change in Asthma Control Questionnaire (ACQ) scores from baseline to 12 months. Participants (mean [SD] age, 47.6 [12.4] yr) were 70.6% women, 20.0% non-Hispanic black, 20.3% Hispanic/Latino, and 8.2% Asian/Pacific Islander. At baseline, they were obese (mean [SD] body mass index, 37.5 [5.9] kg/m(2)) and had uncontrolled asthma (Asthma Control Test score, 15.1 [3.8]). Compared with control subjects, intervention participants achieved significantly greater mean weight loss (±SE) (intervention, -4.0 ± 0.8 kg vs. control, -2.1 ± 0.8 kg; P = 0.01) and increased leisure-time activity (intervention, 418.2 ± 110.6 metabolic equivalent task-min/wk vs. control, 178.8 ± 109.1 metabolic equivalent task-min/wk; P = 0.05) at 12 months. But between-treatment mean (±SE) differences were not significant for ACQ changes (intervention, -0.3 ± 0.1 vs. control, -0.2 ± 0.1; P = 0.92) from baseline (mean [SD], 1.4 [0.8]), nor for any other clinical asthma outcomes (e.g., spirometric results and asthma exacerbations). Among all participants regardless of treatment assignment, weight loss of 10% or greater was associated with a Cohen d effect of 0.76 and with 3.78 (95% confidence interval, 1.72-8.31) times the odds of achieving clinically significant reductions (i.e., ≥0.5) on ACQ as stable weight (<3% loss or gain from baseline). The effects of other weight change categories were small.

Conclusions: Moderately and severely obese adults with uncontrolled asthma can safely participate in evidence-based lifestyle intervention for weight loss and active living. The modest average weight and activity improvements are comparable to those shown to reduce cardiometabolic risk factors in studies of similar interventions in other populations but are not associated with significant net benefits for asthma control or other clinical asthma outcomes in the current population. Instead, weight loss of 10% or greater may be required to produce clinically meaningful improvement in asthma. Clinical trial registered with www.clinicaltrials.gov (NCT00901095).

Keywords: adults; asthma; clinical trial; exercise; weight loss.

Figure 1.

Participant flow. *The Asthma Control Questionnaire (ACQ) score was computed as the mean of the complete seven-item scores (ACQ7) or the six-item scores (ACQ6) if FEV₁ was missing because spirometry was not performed or not usable per American Thoracic Society standards.

Figure 2.

Categorical weight loss at 6 and 12 months in the intention-to-treat population. (A) Percentage of participants with ≥5% loss of baseline weight. (B) Percentage of participants with ≥7% loss of baseline weight. (C) Percentage of participants with ≥10% loss of baseline weight.

Figure 3.

Correlations between change in Asthma Control Questionnaire (ACQ) scores and percentage weight change from baseline to 12 months among all participants. (A) Correlation between change in ACQ scores and continuous percent weight change. (B) Correlation between change in ACQ scores and categorical percent weight change.