Peer weight norm misperception as a risk factor for being over and underweight among UK secondary school students

Background: Erroneous perceptions of peer weight norms may be important risk factors for being underweight and overweight. This study assessed misperceptions of peer weight norms and their association with being overweight or underweight among UK youth. Methods: Anonymous surveys were conducted among students (n=2104) attending schools in a Greater London borough in Fall 2007. Students' perceptions of the weight norm for same sex peers in their year in their school (years 5 through 11) are compared with the aggregate self-reports of weight for these same sex and year cohorts in each school. Variation in perceptions is compared with personal body mass index (BMI) on the basis of self-reported height and weight. Results: A total of 34% of males and 32% of females overestimated peer weight norms by more than 5% (10 kg on average). Similarly, 37% of males and 43% of females underestimated peer weight norms by more than 5% (7 kg on average). For both males and females, overestimating peer weight norms was associated with a greater risk for being overweight and underestimating peer weight norms was associated with a greater risk for being underweight. Perceived peer weight norm was the strongest predictor of BMI among females compared with estimated actual weight norms of peers (based on the mean of self-reported weight) and demographic factors, and one of the two strongest predictors among males in linear regression analyses, including schools as fixed effects. Conclusions: Pervasive misperceptions of peer weight norms may contribute to unhealthy weight-related behaviors and help perpetuate students' overweight or underweight status. Future research should examine perceptions of other weight-related peer norms and explore what may create misperceptions. Addressing pervasive misperceptions of weight could perhaps be included as a part of interventions aimed at reducing unhealthy weight and related behaviors. European Journal of Clinical Nutrition (2010) 64, 965-971; doi:10.1038/ejcn.2010.106; published online 14 July 2010