Psychosocial functioning in the obese before and after weight reduction: construct validity and responsiveness of the Obesity-related Problems scale.

OBJECTIVE: The Obesity-related Problems scale (OP) is a self-assessment module developed to measure the impacts of obesity on psychosocial functioning. Our principal aim was to evaluate the construct validity and responsiveness of the OP scale. Our specific aims were to test: (1). the psychometric performance of OP; (2). if OP scores differed by gender and weight category; (3). if OP scores are inversely related to mental well-being; (4). if weight reduction in the obese is accompanied by improvements in psychosocial functioning (OP).
SUBJECTS: Four samples were used: 6863 subjects in the SOS cross-sectional study; 2128 in the SOS intervention study; 1017 nonobese in the SOS reference study; and 3305 obese subjects in the XENDOS study. MEASUREMENTS: Psychosocial functioning was measured by OP. Overall mood was measured by MACL. Anxiety and depression symptoms were measured by HAD.
RESULTS: Psychometric testing provided strong support for the construct validity of OP. Factor analysis confirmed the homogeneity of the construct and multitrait/multi-item scaling analysis demonstrated strong item-convergent/discriminant validity. Reliability coefficients were high and floor and ceiling effects were small. Psychometric results were cross-validated and replicated in subgroups by gender, age and body mass index (BMI). As expected, large differences in OP were observed between obese and nonobese (P<0.0001). Obese women reported more weight-related psychosocial problems than obese men (P<0.0001). Psychosocial disturbances (OP) among the obese were significantly related to poor mood (MACL; P<0.0001) and anxiety and depression symptoms (HAD; P<0.0001). Change in OP over time was strongly correlated with weight loss (P<0.0001). A distinct dose-response effect between weight reduction and improvements in OP was demonstrated. Scores on psychosocial functioning (OP) and mental well-being (MACL, HAD) in nonobese (BMI<30) surgical patients at 4-y follow-up were equal to scores observed in nonobese reference subjects (NS).
CONCLUSION: OP is a psychometrically valid obesity-specific measure suitable for evaluating HRQL effects of obesity interventions. The negative impact of obesity on psychosocial functioning is considerable and disturbances are connected with poor mental well-being. Weight reduction in the obese is followed by improvements in both psychosocial functioning and mental well-being.