America’s Obesity Crisis Is Much Worse Than You Think, Researchers Warn
Under a new definition of obesity endorsed by orgs including The American Heart Association, 70% of Americans are considered obese, up from an already problematic 40%
It’s not uncommon to hear scientists and medical professionals warn about the dangers of America’s obesity epidemic. While there are debates about the best approaches to treat obesity, practitioners are also reconsidering how exactly obesity should be defined — and researchers have just found that changing that definition could dramatically increase the percentage of U.S. adults diagnosed with obesity.
In a new study published in the journal JAMA Network Open, researchers applied the expanded definition to a population of over 300,000, finding that the prevalence of obesity jumped from about 40% to almost 70%, and affected nearly 80% of adults over 70.
“We already thought we had an obesity epidemic, but this is astounding,” said co-first author Lindsay Fourman, MD, an endocrinologist in the Endocrinology Division of the Mass General Brigham Department of Medicine. “With potentially 70% of the adult population now considered to have excess fat, we need to better understand what treatment approaches to prioritize.”
Obesity Under the New Definition
Under the new definition, someone is considered to have obesity if they have a high BMI plus at least one elevated anthropometric measure, what researchers call “BMI-plus-anthropometric obesity.” Others can also be considered to have obesity if they have a normal BMI plus two elevated anthropometric measures (called “anthropometric-only obesity”). Those anthropomorphic measures include factors like waist circumference, waist-to-height ratio and waist-to-hip ratio.
Researchers have found that the move beyond BMI provides a better picture of the fat adipose tissue distribution and helps differentiate between muscle and fat mass, two factors that can indicate metabolic risk.
“We have always recognized the limitations of BMI as a single marker for obesity because it doesn’t take into account body fat distribution,” said senior author Steven Grinspoon, MD, and chief of the Metabolism Unit in the Endocrinology Division of Mass General Brigham.
Notably, the study also found that those diagnosed with anthropometric-only obesity — who have a normal BMI but other risky body composition factors — had a higher risk of diabetes, cardiovascular disease, and mortality than people without obesity. The study authors emphasize, however, that more research is needed to better understand the causes of anthropometric-only obesity and best methods of treatment.
The reworked definition also distinguishes between preclinical and clinical obesity, with clinical obesity considered the presence of obesity-related physical impairment or organ dysfunction.
The American Heart Association and The Obesity Society are among 76 organizations that have endorsed the expanded definition.
“Identifying excess body fat is very important as we’re finding that even people with a normal BMI but with abdominal fat accumulation are at increased health risk,” Fourman added. “Body composition matters – it’s not just pounds on a scale.”
An Opportunity for Fitness?
The rise of obesity diagnoses and GLP-1 use has proven to offer a new opportunity for the fitness industry to support those undergoing a weight-loss journey as well. A 2024 report revealed that the total addressable market for U.S. fitness clubs — including gyms and boutique studios — was expected to increase by $6.8 billion as a result of more people taking GLP-1s.
The report’s authors hypothesized that as more Americans shift to GLP-1s for weight loss or obesity treatment, the more inclined they become to join a gym or adhere to a fitness program.