Overestimation and underestimation: adolescents' weight perception in comparison to BMI-based weight status and how it varies across socio-demographic factors.

BACKGROUND: Weight perception has been studied with a limited focus on "feeling overweight." This study, using a more inclusive definition of overestimation and underestimation, examines adolescents' weight perception focusing on how accurate it is in relation to body mass index (BMI)-based weight status and how it varies across socio-demographic factors.
METHODS: Data are from the 2007 Minnesota Student Survey, a paper-and-pencil survey completed in the classroom by students in public schools. The final analyses were based on the data from 87,418 high school students who were asked about their height and weight.
RESULTS: Weight perception and the BMI-based weight status (based on self-reported weight and height) were strongly and positively correlated, but substantial discordance was observed with more than a quarter of the students (27.6%) having discordant weight perception. Males, minorities, and those from low-income households were more likely than their respective counterparts to have a discordant weight perception. Overall, underestimation was more prevalent than overestimation. Girls were more likely to overestimate, while boys were more likely to underestimate. Black and Hispanic females and those from low-income households were more likely to underestimate than overestimate their weight, while Asian/Pacific Islander males were more likely to overestimate than underestimate.
CONCLUSIONS: If underestimation is more prevalent among Black or Hispanic females and those from low-income households, the already higher prevalence of obesity among these groups is unlikely to decrease. Overestimation, on the other hand, can be a risk factor for unhealthy weight-control behaviors. Monitoring adolescents' perceived weight in addition to their BMI is critical to understanding the challenge we face with childhood obesity.