Nonreporting of body mass index: a research note on the interpretation of missing data

The aim of the study was to investigate the correlates of missing values on body mass index (BMI), with a view to distinguishing between potential hypotheses as to their origin.

Participants were 1,452 secondary school students who completed questionnaire measures of BMI, perceived weight, body dissatisfaction, appearance investment, and eating disorder symptomatology.

More than one fourth of the sample had missing values on height or weight, the highest proportion of missing data occurring among older girls. Missing status on weight was associated with poorer body image and a greater investment in appearance for girls, but not for boys.

It was concluded that the pattern of results was most consistent with the hypothesis that missing values resulted from motivated nonresponding. More generally, the study provides an illustration of the usefulness of treating missing values as data in their own right.