Validation of a parent-proxy, obesity-specific quality-of-life measure: sizing them up

The aims of the present study were to develop and validate a new obesity-specific, parent-proxy measure of health-related quality of life (HRQOL), Sizing Them Up. Participants included 220 obese youth (M(age) = 11.6 years, 68% female, 53% African American, M(BMI) = 36.7) and their primary caregivers (88% mothers). Primary caregivers completed a demographics questionnaire and two HRQOL measures: Sizing Them Up (obesity-specific) and PedsQL (generic). Youth height and weight were measured. Psychometric evaluation of Sizing Them Up was completed by conducting a factor analysis and determining internal consistency coefficients, test-retest reliability, convergent and discriminant validity, predictive validity, responsiveness to change, and minimal clinically important difference (MCID) scores. Sizing Them Up is a 22-item measure with six scales (i.e., Emotional Functioning, Physical Functioning, Teasing/Marginalization, Positive Social Attributes, Mealtime Challenges, and School Functioning) that account for 66% of the variance. The measure also includes an Adolescent Developmental Adaptation module. Sizing Them Up had internal consistency coefficients ranging from 0.59 to 0.91 and test-retest reliabilities ranging from 0.57 to 0.80. Validity was demonstrated by significant relations between a majority of Sizing Them Up scales and BMI z-scores. Sizing Them Up also demonstrated good convergent validity with other HRQOL measures and responsiveness to change related to weight loss for adolescents who had undergone bariatric surgery. Overall, Sizing Them Up is a reliable and valid parent-proxy measure of obesity-specific HRQOL that can be used in both clinical and research settings.