BMI-based body size guides for women and men: development and validation of a novel pictorial method to assess weight-related concepts

Objectives: To develop and evaluate two BMI-based instruments to determine perceptions of weight status, particularly perceptions of overweight and obesity, using pictorial images of women and men. Methods: Pictures of adults with known BMI values were used to construct gender-specific body size guides (BSGs) containing 10 bodies that ranged from underweight to class III obesity. Figures were standardized and a composite face was added to each. The BSGs were administered to 400 adults to assess the psychometric properties of the instruments and weight perceptions. Results: High correlations between the BMIs of respondents and the BMIs of the current body selected by respondents provided strong support for the criterion-related validity of the BSGs, and the logical pattern of responses to items assessing perception of weight categories supported construct validity for the scales. Test-retest reliability, assessed by correlations for both current and ideal body, was also high, despite the lengthy 6-month testing interval. Respondents' perceptions of the bodies within specific weight categories indicated that a majority failed to recognize the overweight female as overweight and perceived the overweight male as normal weight. Obese bodies were generally unrecognized as such until the bodies reached the higher levels of obesity (that is, BMI values 439). Perception of weight was influenced by the respondents' weight status and gender. Conclusions: Psychometric analyses indicated the BSGs are valid and reliable instruments. These results, coupled with the face validity of the scales and the relationship between the bodies and BMI values, indicate the BSGs offer advantages over existing instruments for researchers of weight perception and body image. Administration of the scales to an adult sample confirmed that overweight and obesity are under-recognized. Increased efforts to improve public understanding of these terms are needed and the BSGs may provide useful tools for this purpose.