Validating Sizing Them Up: A parent-proxy weight-related quality-of-life measure, with community-based children

Background/Objective: A weight-related Quality of Life (QoL) questionnaire elicits parents’ perceptions to understand the impacts of weight on children's QoL. Sizing Them Up, a parent-proxy of a weight-related instrument, is a proper measure for the purpose, but its psychometric properties have not been validated on a non-clinical child population. This study aimed to thoroughly examine the psychometric properties of the Sizing Them Up on a non-clinical child population. Methods: Children from Taiwan (M(age) = 11; SD = 1.02; N = 236) filled out a weight-related QoL instrument (Sizing Me Up) while their parents completed Sizing Them Up and two generic QoL instruments. Confirmatory factor analysis (CFA), concurrent validity, and known-group validity were conducted. Results: CFA supported the factor structure of Sizing Them Up. The concurrent validity of the Sizing Them Up total score was satisfactory: r = .46 to .53 with other QoL instruments. Known-group validity was supported as obese children had significantly lower Sizing Them Up total score than did normal-weight and underweight children. Conclusions: We extended the use of Sizing Them Up from clinically obese children to a community-based sample of underweight as well as overweight children. Healthcare providers may use Sizing Them Up to measure the weight-related QoL for children.