Psychometric and cross-national evaluation of a Portuguese version of the Impact of Weight on Quality of Life-Lite (IWQOL-Lite) questionnaire

Objective: To evaluate the properties of a Portuguese version of the Impact of Weight on Quality of Life-Lite (IWQOL-Lite) questionnaire and to compare quality of life scores between samples of Portuguese and American women. Research Methods and Procedures: IWQOL-Lite scores were obtained from 138 Portuguese participants who were enrolled in a 2-year lifestyle weight management programme ('Portuguese clinical sample') and 250 Portuguese volunteers from the community ('Portuguese community sample'). Subjects were matched on gender (all female), BMT, age and treatment-seeking status to American individuals from the IWQOL normative database who completed the IWQOL-Lite in English. In addition, Portuguese community subjects completed the SF-36 and their scores were compared to American individuals' scores from the normative database. The psychometric properties of the Portuguese version of the IWQOL-Lite were determined, and Portuguese and American samples were compared on quality of life. Results: The Portuguese and English versions of the lWQOL-Lite appeared psychometrically very comparable. The Portuguese IWQOL-Lite demonstrated excellent psychometric properties (internal consistency, correlations with BMI, factor structure, correlation with SF-36, discriminant validity). Comparison of Portuguese and American subjects suggested that increasing BMI may have a more adverse effect on quality of life in Portuguese individuals as compared to Americans. Discussion: The results suggest that the Portuguese translation of the IWQOL-Lite is a reliable and valid measure of obesity-specific quality of life. Obesity may have a greater impact on quality of life in Portuguese women compared to American women. Copyright (c) 2005 John Wiley & Sons, Ltd and Eating Disorders Association.