Validation of the modified weight bias internalization scale in a Spanish adult population

Weight bias internalization has received considerable attention in recent years and has been associated with serious psychological and physical consequences in Westernized societies. The modified weight bias internalization scale (WBIS-M) is one of the most frequently used instruments for assessing internalized weight stigma across different body weight categories. The aim of this study was to adapt the WBIS-M for use in Spanish adult populations. The sample consisted of 678 participants from the Spanish general population recruited through the internet, 79.6% of whom were women. The scale was translated into Spanish and then backtranslated. To study the internal structure, a cross-validation analysis was carried out including both exploratory and confirmatory factor analyses to assess the scale's psychometric properties. Internal consistency was evaluated using Cronbach's alpha and McDonald's omega and a test-retest was conducted to assess one-month stability. Results confirmed that the Spanish adaptation of the WBIS-M is an 11-item unidimensional scale, like the original version and shows excellent psychometric properties. In conclusion, the Spanish WBIS-M version seems to be a robust psychometric tool for use in clinical and research settings.