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 (alpha 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 (alpha = 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 > or = 2.5% weight loss of 0.77 for the OWLQOL and -0.54 for the WRSM. At > or = 50 weeks for > or = 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.