A new study from Mass General Brigham shows that a recent update to how obesity is defined could mean nearly 70% of American adults are now considered to have the condition. This is a big jump from the previous estimate of about 40%.
The updated definition comes from the Lancet Diabetes and Endocrinology Commission and was analyzed using health data from over 300,000 people. The biggest increases were seen among older adults. The study was published in the journal JAMA Network Open.
Obesity has long been defined using body mass index, or BMI, which is based on a person’s height and weight. But experts now say that BMI alone may miss some important signs of health problems.
BMI doesn’t show where fat is stored in the body or how much of a person’s weight is muscle versus fat. That’s why researchers are now using extra tools—like measuring waist size and how it compares to a person’s height or hips—to get a better idea of health risks.
Under the new definition, a person can be labeled as having obesity in two ways. One group includes people with a high BMI and at least one other body measurement that is too high. This is called “BMI-plus-anthropometric obesity.” A
nother group includes people with a normal BMI but with at least two body measurements that show too much fat. This group is called “anthropometric-only obesity.” Obesity can also be categorized as “clinical” if it causes physical problems or organ damage. These new ideas are already supporte…
When researchers applied these updated standards to a large national health database, they found that 68.6% of people met the new definition of obesity.
That’s compared to just 42.9% using only BMI. The increase was mostly from people who would not have been considered obese under the old rules, but who now qualify due to their body fat distribution.
The study also showed that these newly labeled individuals face real health risks. People in the “anthropometric-only” group had higher rates of heart disease, diabetes, and even death than people without obesity.
Interestingly, about half of all people who now meet the new obesity definition were found to have clinical obesity, meaning their condition was already affecting their health.
Age made a big difference too. Nearly 80% of adults over the age of 70 met the new criteria for obesity. Differences were also found between men and women and across different racial groups, but age had the biggest impact.
Doctors say this new way of defining obesity could help them better understand who is at risk and which treatments to use. Many people who were once considered healthy based on BMI alone may actually be at risk due to where they carry fat on their bodies.
Dr. Steven Grinspoon, a senior author of the study, explained that BMI has always had its limits because it doesn’t show how fat is spread out in the body. He said this study proves that people with normal weight but high levels of belly fat may still face serious health problems.
This raises important questions about whether these people should receive obesity treatments, including medication.
The research team says more studies are needed to understand why this type of obesity happens and how best to treat it. They’ve already created a therapy aimed at reducing waist size and want to see if it works well for people in this newly recognized group.
Dr. Lindsay Fourman, another author of the study, said that focusing on body fat and where it is stored is key. “It’s not just about how much you weigh,” she said. “It’s about what kind of fat you have and where it is.”
This new understanding of obesity may help doctors catch health risks earlier and offer better care to people who didn’t previously fit the standard definition. It could also lead to better ways to treat and prevent serious health problems linked to body fat.
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