Challenges of Accurately Measuring and Using BMI and Other Indicators of Obesity in Children

Abstract

BMI is an important indicator of overweight and obesity in childhood and adolescence. When measurements are taken carefully and compared with appropriate growth charts and recommended cutoffs, BMI provides an excellent indicator of overweight and obesity that is sufficient for most clinical, screening, and surveillance purposes. Accurate measurements of height and weight require that adequate attention be given to data collection and management. Choosing appropriate equipment and measurement protocols and providing regular training and standardization of data collectors are critical aspects that apply to all settings in which BMI will be measured and used. Proxy measures for directly measured BMI, such as self-reports or parental reports of height and weight, are much less preferred and should only be used with caution and cognizance of the limitations, biases, and uncertainties attending these measures. There is little evidence that other measures of body fat such as skinfolds, waist circumference, or bioelectrical impedance are sufficiently practicable or provide appreciable added information to be used in the identification of children and adolescents who are overweight or obese. Consequently, for most clinical, school, or community settings these measures are not recommended for routine practice. These alternative measures of fatness remain important for research and perhaps in some specialized screening situations that include a specific focus on risk factors for cardiovascular or diabetic disease. ]) has probably become the most common indicator used to assess overweight and obesity in a wide variety of settings, including clinical, public health, and community-based programs. Although it is certainly not a perfect surrogate for total body fatness and not without its technical limitations, 1 BMI has been recommended as the most appropriate single indicator of overweight and obesity in children and adolescents outside of research settings. [2][3][4] One of the attractive features of BMI is that it is derived from measurements of height and weight. These 2 anthropometric dimensions are the ones most commonly collected on children worldwide. These 2 measurements are noninvasive, relatively inexpensive to obtain, and relatively easily understood by health practitioners, the individuals being measured, and their families.Mentioning child measurements of height and weight, individuals may be reminded of their own marks on the door sills and the bathroom scales of their childhood homes. So, although wide familiarity with height and weight enhances the use and understanding of a measure such as BMI, it also may desensitize health professionals to the need to give adequate attention to issues concerning how height and weight data are collected. Accordingly, one may hear the comment, "Anyone can measure height and weight." Although one must actually agree with the language, if not the intent, of this easy declaration, many health professionals are unaware that there are consequences for the usefulness and ac...

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