Seventy-five percent of adults in the United States would be classified as obese under a new obesity index that integrates various body measurements with the traditional body mass index (BMI). This updated classification, introduced by the Lancet Diabetes and Endocrinology Commission in January 2024, aims to provide a more comprehensive understanding of obesity, which has become an escalating health issue globally.
According to a recent study published in the Journal of the American Medical Association (JAMA), the new index combines waist circumference, waist-to-hip ratio, and waist-to-height measurements with BMI to offer a more accurate representation of body fat distribution. This approach reveals that four in five U.S. adults classified as overweight based on BMI would actually be deemed obese under the new criteria. Moreover, an alarming 38% of individuals with a “healthy” BMI might also be reclassified as obese.
Historically, the U.S. obesity prevalence was reported at approximately 40% from 2021 to 2023, according to the U.S. Centers for Disease Control and Prevention. The validity of the updated figure has sparked discussions among health professionals.
“I was shocked,” stated Dr. Maria Escobar Vasco, an endocrinologist at UT Health San Antonio. “Obesity is certainly an epidemic, and we’re seeing rising incidence and prevalence of obesity, but 75% seems high.”
Understanding the New Obesity Metrics
Obesity rates in the United States have surged since the introduction of BMI in the early 1970s. This has prompted ongoing dialogue about the multifaceted causes of obesity, the associated stigma, and whether it should be defined as a chronic disease, as recognized by the CDC and the American Medical Association.
Dr. Aaron King, a family medicine physician, emphasized the challenges in interpreting the 75% figure, noting that a universally accepted definition of obesity is lacking. “When you draw the line, that’s always a question that is up for a little bit of debate,” he explained. “But if you’re asking whether 75% of U.S. adults are at high risk for developing metabolic disease, the data suggests yes.”
The inadequacies of BMI as a standalone metric are increasingly recognized. The BMI formula calculates weight in kilograms divided by height in meters squared, categorizing individuals with a BMI of 30 or above as obese. However, it does not differentiate between body fat and muscle mass, leading to both overestimations and underestimations of obesity.
For instance, as Dr. King pointed out, a weightlifter with a BMI above 30 may be classified as obese despite having a low body fat percentage. Conversely, individuals with a BMI around 25 might have a significant amount of visceral fat, putting them at higher risk for various diseases.
Visceral fat, also referred to as truncal obesity, is particularly linked to conditions such as insulin resistance and cardiovascular disease. In contrast, fat stored around the hips and thighs, known as gluteofemoral fat, is considered protective against metabolic disorders.
Implications for Health Care and Insurance
The Lancet Commission aims to rectify these shortcomings in BMI by incorporating additional measurements to enhance risk assessment for diseases. “The distribution of fat makes a difference,” Dr. Escobar noted. “Excess fat in the abdominal area can affect critical organs like the liver, leading to conditions such as fatty liver disease.”
Those classified within the normal BMI range but identified as obese according to the new index may face challenges accessing necessary medications, as insurance often requires meeting specific BMI thresholds. This issue is particularly pronounced among Asian Americans, for whom researchers recommend adjusted BMI thresholds to facilitate earlier access to treatments.
The Commission differentiates between pre-clinical obesity, characterized by excess fat without functional impairment, and clinical obesity, which is marked by systemic health alterations due to excessive adiposity. However, the JAMA study combines these two categories, highlighting the need for further research.
Despite its limitations, BMI remains a widely utilized screening tool in clinical settings due to its simplicity and cost-effectiveness. “It’s mainly a convenience factor,” Dr. King remarked, acknowledging that while BMI is not ideal, it is commonly accepted because it allows for quick assessments.
Dr. Escobar added that while BMI can provide a general idea of health status, more precise measures such as waist-to-hip ratios should become standard practice.
The researchers concluded that implementing the new obesity measurement will require robust education for both healthcare providers and the public. “In an ideal world, we would not rely on BMI,” Dr. King stated. “But transitioning away from it will likely be a gradual process.”
As discussions about obesity and its implications continue, the health community acknowledges the importance of refining criteria to better address this critical public health issue.
