The validity of self-reported weight change among adolescents and young adults.

OBJECTIVE: To assess the association of weight change based on serial self-reported vs. measured weights. RESEARCH METHODS AND PROCEDURES: Two thousand two hundred eighty-four male and 2,476 female participants in the National Longitudinal Study of Adolescent Health who provided information on weight at Waves II and III and were at least 16 years of age were studied. Linear regression was used to assess predictors of the discrepancy between weight change based on self-reported vs. measured weights. Logistic regression was used to identify predictors of self-report correctly classifying participants in terms of weight change category.
RESULTS: Self-reported weight was slightly lower than measured weight at Waves II and III, but weight change based on self-reported weights underestimated true weight change by only 2.1 (female participants) to 2.8 (male participants) pounds. Overweight and obese female participants were consistent in their under-reporting of their weight more than their leaner peers; thus, the discrepancy between weight change from Wave II to Wave III based on serial self-reports vs. measured weights was significantly smaller among the obese female vs. healthy-weight female participants (0.3- vs. 2.3-pound underestimation, p < 0.05). Among the male participants, the same pattern was evident. African-American ethnicity, Hispanic ethnicity, the level of physical activity, the hours per week watching television, and weight change efforts were not related to the discrepancy between weight change based on self-reported vs. measured weights. DISCUSSION: The discrepancy between weight change based on self-report vs. measured weights was minor and not related to race, weight change efforts, activity, or inactivity, thus suggesting that much of the error is random.