Determinant factors of the difference between self-reported weight and measured weight among Japanese.

Objectives: To assess the difference between self-reported and measured weight values in Japanese men and women and to determine the underlying determinants of the differences between self-reported and measured values.

Methods: The data were collected from 363 general Japanese individuals aged 16-88 years living in Kumamoto prefecture. Participants completed a self-administered questionnaire designed for this study with self-reported weight and height values. Measured weight and height were measured immediately after questionnaire completion. Paired t-tests identified differences between self-reported and measured values by sex. Multiple-stepwise regression analysis examined the independent variables' effects on the differences between self-reported and measured weights.

Results: Significant differences were found between self-reported and measured values for both sexes (p < 0.001). There was a significant negative relationship between the difference in an individual's self-reported and measured weight in each sex, with higher measured weight individuals more likely to underestimate their weight. Multiple-stepwise regression analysis models explained 12.1 % (p < 0.01), 11.3 % (p < 0.01), and 5.6 % (p < 0.01) of the variance in all participants, men, and women, respectively. Significant effects were found for age, weight measurement frequency, and measured weight in total participants, weight measurement frequency, and measured weight for men, and age for women.

Conclusions: In this study, the mean absolute value of the weight and height variances proved the unreliability of self-reported weight and height values. This study's findings suggest self-reported weight inaccuracy especially for obese populations. This should be adjusted when using it in epidemiological studies and healthcare planning.