New Obesity Criteria Could Classify Nearly 70% of Americans as Obese

New research from Mass General Brigham is set to dramatically reshape how obesity is defined in the United States, potentially classifying nearly 70% of American adults as obese. The proposed update, published in JAMA Network Open, moves beyond the traditional Body Mass Index (BMI) metric to incorporate waist measurements and body fat distribution as key indicators of health risk.

After examining data from approximately 300,000 people, researchers found that the estimated obesity rate in the U.S. would surge from the current 42.9% to almost 70% under the new criteria. This significant increase highlights the limitations of using BMI alone as a health indicator.

“We already thought we had an obesity epidemic, but this is astounding,” said Dr. Lindsay Fourman, an endocrinologist in the Mass General Brigham Department of Medicine and co-first author of the study. “With potentially 70% of the adult population now considered to have excess fat, we need to better understand what treatment approaches to prioritize.”

The new benchmarks are particularly impactful for older demographics. Nearly 80% of study participants over age 70 met the obesity classification under the revised criteria, according to the researchers.

Medical experts have long recognized that where fat is stored on the body is often more important than overall weight in predicting health outcomes. Abdominal fat accumulation, known as visceral fat, is particularly concerning because it surrounds internal organs and is linked to serious health complications.

“Visceral fat has long been recognized as metabolically harmful,” explained Dr. Philip Rabito, a New York City specialist in endocrinology, weight loss and wellness. This type of fat significantly increases the risk of conditions like diabetes, dyslipidemia, hypertension and cardiovascular disease.

The updated definition could identify individuals who have previously been considered healthy by BMI standards but actually face elevated health risks due to their fat distribution. This more nuanced approach might help direct resources toward patients who need intervention despite having a seemingly “normal” BMI.

Dr. Rabito suggested that redefining obesity could help “direct greater clinical attention and resources” to vulnerable populations. Additionally, “more of these patients may become eligible for GLP‑1–based therapies than under prior definitions, with the potential to meaningfully reduce their future cardiovascular risk,” he noted.

The GLP-1 receptor agonist medications, which include popular drugs like Ozempic and Wegovy, have shown significant effectiveness in helping patients lose weight and potentially improve related health conditions.

Texas-based Dr. Mary Claire Haver, a board-certified OBGYN and founder of The ‘Pause Life, said she wasn’t surprised by the findings. “I have been watching this trend unfold in my clinic for years,” she said. “What concerns me most is that headlines like this often rely almost exclusively on weight-based measures such as BMI, which are blunt tools and miss what actually drives long-term health risk.”

Haver emphasized that fat distribution is far more important than weight alone in determining health outcomes. “From a physiologic and metabolic standpoint, fat distribution matters far more than body weight alone,” she explained. Visceral fat is the “primary driver” of insulin resistance, cardiovascular disease, fatty liver disease and inflammatory risk, while subcutaneous fat—visible on the body’s surface—typically carries lower metabolic risk when paired with adequate muscle mass.

This distinction is crucial in clinical practice. “In my patient population, I routinely see individuals who technically meet criteria for obesity based on BMI, but have high lean muscle mass, relatively low visceral fat and excellent metabolic health,” Haver noted. She estimates this group represents approximately 20% of patients labeled as obese in her practice.

While Haver projects that obesity numbers will likely improve with the expanding use of GLP-1 medications, she warns that focusing exclusively on weight can obscure who is truly at risk and contribute to stigma. “Tools that assess body composition, waist circumference and markers of insulin resistance give us a far more accurate picture than the scale ever could,” she concluded.