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The Limitations of BMI in Pediatric Overweight Diagnosis: A Call to Action

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The 2023 Clinical Practice Guideline for Evaluation and Treatment of Children and Adolescents with Obesity heralds a new era of evidence-based anti-obesity treatments for children, a cause I wholeheartedly support. However, amid these advancements, I harbor concerns about the ongoing reliance on the Body Mass Index (BMI) as a screening and diagnostic tool.

Originally designed for population-level assessments, the ease of measuring BMI and its historical precedence have led to its widespread adoption for individual diagnoses. Yet relying solely on BMI can lead to significant inaccuracies, as numerous studies have demonstrated. Surprisingly, research reveals that approximately one-third of children falling within the BMI percentile range of 85th to 94th exhibit normal adiposity levels. This illustrates the limitations of BMI as a diagnostic measure. Compounding the issue is the uneven performance of BMI across different races and ethnicities — an aspect briefly mentioned in the guidelines but deserving of further elaboration. Astonishingly, the positive predictive value of an overweight BMI to predict excess adiposity stands at 65% for white male youth, 52% for white female youth, 36% for Black male youth, and 30% for Black female youth. Such inconsistency raises serious concerns about systemic racism in medicine, compelling us as trusted healers to strive for more accurate and equitable measures.

An inaccurate diagnosis carries practical, psychological, and psychosocial implications. In the current landscape, it triggers immediate referrals for over 26 hours of Intensive Home-Based Lifestyle Therapy, a scarce resource heavily reliant on institutional funding and grants. This situation poses a real risk of harm, particularly when we consider that many white children and the majority of Black children categorized as overweight do not exhibit excess adiposity. It is imperative that we consider the broader ramifications of misdiagnosis and take action to mitigate the potential consequences.

BMI extends its impact beyond the diagnosis of weight status to influence various aspects of individuals' lives. For instance, insurers often employ BMI as a determining factor for life insurance qualifications, affecting coverage eligibility and premium rates. Similarly, in military service, BMI requirements can determine enlistment eligibility and eligibility for specific roles within the armed forces. These examples illustrate how BMI can shape crucial life opportunities, from securing insurance coverage to pursuing desired career paths. However, it is vital to recognize the limitations of BMI as a singular measure, as it may not accurately reflect an individual's overall health or risk factors. Relying solely on BMI can lead to potential inequities and unintended consequences in these spheres of life.

In the realm of life-saving opportunities, the flawed use of BMI becomes even more critical. Take, for example, heart transplant allocation. The allocation of scarce donor organs is a matter of life and death, and BMI sometimes serves as a criteria for determining transplant eligibility. Research has consistently demonstrated that BMI performs differently across races and ethnicities, leading to potential disparities and unequal access to organ allocation. This disparity underscores the urgent need for more accurate and equitable evaluation measures in organ allocation, ensuring decisions are based on comprehensive and fair assessments. 

To address these issues, I recommend utilizing BMI as a starting point for evaluation but not as the sole determinant for diagnosing weight status or determining eligibility for a treatment, program, or service. Clinicians should consider other pertinent factors, including lifestyle habits, risk factors, lean body mass, and, in some cases, measures of adiposity. By adopting a multidimensional approach, we can ensure a fair and accurate assessment and treatment plan for all children.

Natasha Agbai, MD is a pediatrician at Discover Health and founder of Weight Loss For Kids. She shares evidence-based weight management information on her TikTok and Facebook groups.

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