Accuracy of Teen and Parental Reports of Obesity and Body Mass Index

DISCUSSION

This study answers an important question for those studying adolescent obesity—self-reported height and weight can be used to calculate BMI and provide a categorical measure of obesity among teens using the 95% cutoff points. Using this method, over 96% of youth in this large, nationally representative sample were correctly classified. Sensitivity, specificity, positive predictive value, and negative predictive value of obesity by self-reported BMI were all high. This study also showed that adolescent girls were no more likely than boys to be misclassified as obese using self-reported data. No independent correlates of misclassification were identified in the final logistic regression models.

In addition to verifying that BMI from self-reported height and weight is a valid indicator of obesity, these data also provide new important insights into the duality of adolescent obesity—it is both a subjective and objective phenomenon. How this duality impacts on the understanding of obesity by both health care professionals and those impacted by the disease are important areas for discussion and future research. The reasons that adolescents seek treatment for weight concerns are varied. In contrast to adults, referral of adolescents to health care providers is often initiated by parents or by other concerned adults.²⁴ These same adults are also often critical participants in the assessment, diagnosis, and treatment of youth. Thus, although giving adolescents their own voice is a crucial part of caring for youth, understanding and integrating information from multiple informants across diverse environments is an equally important issue in their care.

Research on informant effects comes almost entirely from the literature on emotional and behavioral problems, rather than on health problems such as obesity. Studies of informant differences in the reporting of mental health problems have found that reports of informants show significant agreement, but that levels of agreement vary across different pairs of informants, and self-reports consistently show low agreement with all other informants, including peers.^{24 ,25}Further, cross-informant agreement may be stronger among informants reporting on conduct or externalizing problems, compared with affective or internalizing problems.^24–26 The literature suggests that youth are more likely to report internalizing problems such as depression,²⁶ while parents may be likely to report externalizing problems, such as conduct problems.²⁷

How the current findings on informant differences in obesity fit into this literature is unclear but intriguing. Youth were accurate informants with respect to objective measures of height and weight. However, despite the accuracy of teen reports of height and weight, parents and teens were poor informants with respect to subjective obesity. Parents and teens failed to identify teens that were in fact obese, and incorrectly identified teens as obese, who were not obese. These teens define 2 potential risks groups—those who may not receive needed treatment, and those who may receive inappropriate treatment or may suffer distorted body image. Thus, education of both parents and teens, which addresses both the medical and psychosocial aspects of obesity, may be a necessary prerequisite to medical treatment. Acceptance of the diagnosis and understanding of obesity as a serious health risk may be necessary before actual weight loss protocols can be effective.

Although teens and parents both failed to identify obesity correctly by subjective report, parents were more accurate than teens. This suggests that obesity is akin to externalizing problems, such as conduct problems, which parents are more likely to report and youth are more likely to deny. Indeed, obesity is an observable, external feature. However, as found in the current study, obesity is also a subjective, emotional experience of one's body and body image, and has been significantly associated with internal states, such as lower self esteem²⁸ and experiences of social stigma,^{2 ,3} phenomena for which self-reports are thought to be more reliable.²⁷ Thus, obesity does not fall neatly into objective versus subjective categories. Although it is clearly an objective, measurable phenomenon (eg, BMI), obesity is also socially constructed and has inherent psychosocial implications and psychological meaning for the individual. This subtle interplay of objective and subjective factors in the assessment and treatment of obesity is underscored by the discordance between subjective and objective reports of obesity shown in this study. Obese adolescents may be willing to acknowledge feelings of low self-esteem,²⁸but may be unwilling or unable because of denial and/or stigma, to acknowledge the obesity behind these feelings. In contrast, parents may be better, though imperfect, at reporting subjective obesity.

A parent's ability to report a child as obese may reflect biases resulting from the parent's level of distress or psychological symptoms and/or from labeling of a given teen. For example, parent symptoms in general and maternal depression in particular have been found to be positively related to parent report of child symptoms and depression, respectively.^{25 ,29} Data here suggest that parental report of parent obesity is positively associated with parental report of teen obesity. Whether parental obesity is related to increased accuracy with respect to reporting adolescent obesity is unclear. The impact of parental distress on the subjective identification of teen obesity is also unclear. Because assessment and treatment of obesity often involve parents, how parental weight status, objectivity about weight status, and/or distress regarding weight status interact may be important areas of further inquiry. Parental identification of obesity may be an indicator that the teen's family is concerned about weight status and may be more amenable to intervention than families who do not acknowledge weight problems. Alternatively, parental distress over parental obesity may impact treatment negatively. In addition, discrepancies in adolescent and parental reports of weight problems are certainly a reflection of discrepant perceptions, and may be an indicator of other underlying issues in the parent–teen relationship that can exacerbate the obesity problem.

This study does have several notable limitations. First, Add Health is a comprehensive dataset, but it is school-based and does not include out-of-school youth or school-avoidant youth. Whether obese youth fall into these categories is unclear. A second limitation is that indicators of obesity were not uniformly present in both waves of Add Health. Only adolescent report of height, weight, and weight status were available in both waves of data collection. Parental report of subjective obesity was not available at T2, while measured height and weight were only obtained at this data collection. Third, although an expert panel agreed that BMI ≥95% should define obesity,⁷ a clear standard of 95% cutoff points has not been developed. In an attempt to use the most up-to-date cutoff points, this study used cutoff points determined by a study of standardized measurements of height and weight from 9 large epidemiologic studies.²⁰ A consensus on the appropriate 95% cutoff points would help standardize the field and make findings across studies more comparable.

Despite these limitations, this study has important findings and implications for future research. The social construction of obesity and its impact on treatment is an important area of future inquiry. Although parents and teens functioned poorly as reporters of adolescent obesity, adolescent self-report of height and weight accurately identified >96% of obese adolescents. Findings from other studies that have used self-reported BMI should be considered valid, and future studies can use self-reported data to understand adolescent obesity, its correlates, antecedents, and sequelae.