New Research Indicates Obesity Rates May Be Higher Than Previously Thought

If you’ve ever considered whether you might be classified as obese, now is a good time to reconsider. Recent studies reveal that over two-thirds of Americans could fall into the obese category based on new guidelines—this number is significantly higher than previously reported rates.

A team from Mass General Brigham analyzed health records from a substantial and varied group of Americans. Their findings indicate that nearly 70% meet the updated criteria for obesity, which includes additional metrics beyond just body mass index (BMI). Those categorized as obese under this new definition face a higher risk of health complications than their non-obese counterparts, which, as researchers suggest, could help healthcare providers identify potential issues earlier.

“Our findings suggest that the new obesity definition effectively stratified individuals at high-risk of organ dysfunction and long-term complications,” the authors mentioned in their study, published in JAMA Network Open.

Expanding Beyond BMI

A major coalition of global obesity experts, supported by The Lancet, in January 2025, advocated for a significant shift in diagnosing obesity. This initiative marks a growing effort by some medical professionals and patients to broaden the understanding of what constitutes obesity. Their newly established criteria, released in a report that month, gained support from several health organizations, including the American Heart Association.

Traditionally, BMI, which considers a person’s height and weight, has defined obesity as a BMI of 30 or above. However, the updated guidelines don’t discard BMI entirely. Instead, they encourage practitioners to utilize various other body measurements, such as waist circumference, waist-to-hip ratio, and even DEXA scans, which assess bone density and body fat directly.

The authors of the criteria argued that their revised definition allows doctors to better identify excess body fat, which is a key factor in obesity-related health risks. The new methods aim to better recognize cases of clinical obesity—those most likely to lead to serious health complications. Researchers stated that this is the first comprehensive study exploring the practical effects of implementing these new standards.

Unseen Obesity

The study analyzed information from the All of Us program, a federal effort to gather extensive health data from a diverse demographic in the U.S. They reviewed long-term health outcomes for over 300,000 adults.

Using the previous criteria, about 42.9% of the sample was deemed obese, aligning with national obesity statistics. But under the new criteria, the figure jumped to 68.6%, with 36.1% classified as clinically obese.

Most individuals identified as obese under the old standards also fit the new framework, which incorporates BMI along with additional metrics. Most of the newly classified cases involved individuals who had a “normal” BMI yet registered elevated levels in other measurements. Notably, those with atypical obesity risk still exhibited a greater likelihood of organ dysfunction and diabetes compared to those not categorized as obese with the latest definition. However, classic obesity still appears to carry a higher risk for these health issues compared to the new obesity classification.

The results suggest that the new criteria won’t exclude anyone who would have been diagnosed under the previous system, a conclusion supported by other recent studies. This update should aid doctors in identifying individuals with hidden obesity and excess body fat, potentially leading to earlier interventions for obesity-related complications like diabetes.

“Recognizing excess body fat is crucial because we are discovering that individuals with a normal BMI but significant abdominal fat are at an increased health risk,” stated Lindsay Fourman, a co-lead author and endocrinologist at Mass General Brigham’s Department of Medicine. “Body composition matters—it’s more than just a number on a scale.”

However, implementing this new approach could come with its challenges. For instance, the authors noted that about a quarter of those classified with clinical obesity might not qualify for newer obesity treatments, like GLP-1 therapy. While clinical trials demonstrate the effectiveness of these drugs for traditional obesity cases, it remains uncertain how well they will work for individuals who don’t meet the conventional obesity criteria.

“Thus, the adoption of this framework could have significant implications for patients, especially for current users of GLP-1 medications, and underscores the importance of evaluating the use of anti-obesity treatments in this newly defined group,” they concluded.