Psychometric evaluation of a Brazilian version of the impact of weight on quality of life (IWQOL-Lite) instrument.

Purpose: The impact of weight on quality of life (IWQOL-Lite) is a self-administered instrument that assesses quality of life in obesity. It is composed of 31 items and five domains (physical function, self-esteem, sexual life, public distress, and work). The aim of the present study was to evaluate reliability (test-retest), internal structure, construct validity and discriminant validity.

Methods: IWQOL-Lite scores were obtained from 89 people in a Weight Watchers institution (clinical sample) and 156 community volunteers (community sample). The participants were selected based on the same criteria: gender (female) and age (> 24 years), except for BMI. The community sample also completed the SF-36, a generic measure of health-related quality of life.

Results: The Brazilian IWQOL-Lite demonstrated good test-retest reliability, internal consistency, discriminative validity and convergent validity.

Conclusions: The IWQOL-Lite is the first specific instrument validated in Brazil for assessing quality of life in obesity. The results reveal that IWQOL-Lite is an instrument with good psychometric properties. Nevertheless, in some cases results were dissimilar to those reported in earlier studies using the original American English.