Performance of Two Self‐Report Measures for Evaluating Obesity and Weight Loss *

Objectives : To evaluate performance of the Obesity and Weight‐Loss Quality‐of‐Life (OWLQOL) and Weight‐Related Symptoms (WRSM) measures. Research Methods and Procedures : Four studies of obese persons 18 to 75 years of age were analyzed: a 12‐week initial validation study, a clinical trial using blinded endpoint data at 50 to 83 weeks, and community studies conducted in the U.S. and Europe. Fifty‐six initial validation study subjects visited 1 week after screening to evaluate reproducibility. Results : Overall, 6107 obese persons completed one assessment, 291 completed follow‐up at 12 weeks, and 642 at >50 weeks. Psychometric analyses resulted in a 17‐item OWLQOL with a single score tested on five samples that was internally consistent (α values > 0.90) and reproducible (intraclass correlation coefficient > 0.95). The OWLQOL score (higher is better) was associated, as expected, with the symptom measure (lower is better, −0.54), generic quality of life measure (0.53), and measures of physical (0.40) and mental functioning (0.47). The 20‐item WRSM was internally consistent (α = 0.87) and reproducible (intraclass correlation coefficient = 0.83). The OWLQOL discriminated between genders ( p < 0.001), presence of disability days ( p < 0.05), levels of BMI ( p < 0.05), and levels of symptom bothersomeness ( p < 0.001). Evaluation at 12 weeks yielded an effect size for ≥2.5% weight loss of 0.77 for the OWLQOL and −0.54 for the WRSM. At ≥50 weeks for ≥10% weight change, effect sizes were 1.63 and −0.73, respectively. Discussion : The OWLQOL and WRSM are brief, valid, reproducible, and responsive self‐reported outcomes for evaluating obesity and weight loss.