According to the National Institutes of Health (NIH), US, approximately 42.4% of US adults have obesity. However, this number can increase further as a recent study suggests a new definition of what might be considered as obese. As per the new definition, almost 70% of US adults will be considered obese. The research is published in the journal Jama Network Open by Dr Lindsay Fourman, the first author of the study, from Mass General Brigham in the US. What has changed?The traditional definition of obesity was based on having a body mass index or BMI of 30 or greater, which has been contentious. This is also because it fails to differentiate between fat and muscles. To address the growing obesity crisis, medical experts worldwide proposed a new definition earlier this year. The revised criteria would include people with a BMI over 40, or those with elevated readings for waist size, waist-to-hip, or waist-to-height ratio—either alongside a high BMI or in multiple raised measures, regardless of BMI.Another change brought in was to categorize obesity into two:1. Clinical obesity, where there are signs of illness2. Pre-clinical obesity, where there are no signs of illnessAs per this revamped definition, notes Fourman, there has been increase in obesity prevalence in the US. It means people who were earlier not considered obese as per their BMI, will not fall under this category. What The Expert Explains“Recognizing people with [this type of] obesity can lead to more accurate health risk stratification,” she said. “For example, someone with BMI 23 but excess abdominal fat could benefit from lifestyle interventions such as improving diet and increasing physical activity, even though their BMI is in the “normal” range. Their physician might also more closely monitor for obesity-related complications such as pre-diabetes or fatty liver.”How Was The Study Conducted?The researchers applied both the traditional and newly proposed definitions of obesity to data from 301,026 U.S. adults aged 18 to 80, who participated in a national health study between May 2017 and September 2023.Using the standard BMI data, 43%, which means 128,992 participants were now classified obese. However, as per the new definition, it has gone up to 65%, making it 206,361 participants. It is a nearly 60% jump. Among adults aged 70 and older, the obesity prevalence is at 78%. Almost everyone identified as obese by the traditional BMI measure also met the new criteria, with only 678 individuals no longer classified as such. Notably, the updated definition captured an additional 78,047 participants who would not have been considered obese under BMI alone.“Our data show that these individuals have a heightened risk of organ dysfunction and long-term health complications, suggesting that their classification as having obesity is clinically appropriate,” said Fourman.Of those who were now defined obese without a high BMI, 48% had clinical obesity. 56% of them were those who had obesity based on their BMI together with other measures.