Validity of adult lifetime self-reported body weight.

OBJECTIVE: To investigate the accuracy of self-reported weight status over the adult lifespan.
DESIGN: Estimates of self-report bias were obtained from a linear regression analysis and the magnitude of the discrepancy was studied for demographic groups (based on gender, race and educational attainment), weight status, number of years from the age of the reported weight and current age of the respondent.
SUBJECTS: A subset of 6101 individuals from the National Health and Nutrition Examination Epidemiological Follow-Up constituted the study sample.
RESULTS: Gender, elapsed time and BMI contributed to self-report bias. Effects of gender and elapsed time were small relative to the effects of BMI, with women tending to underestimate weight by 0.82 kg (1.8 lb), men overestimating by 2.27 kg (5.0 lb) and bias increasing by 0.09 kg (0.2 lb) for each year of retrospection. Every increase of one unit in BMI was associated with an additional 0.91 kg (2.0 lb) underestimate in self-reported weight.
CONCLUSION: Accuracy of adult self-reported weight profiles will be greatly underestimated if samples have individuals of current or past high relative weight. Adjusting for underestimation based on the respondent's weight status alone will considerably improve the validity of weight information.