Body mass index might be a more accurate measurement than commonly thought. New research shows that a vast majority of people with a BMI signifying obesity have substantial excess body fat.
Scientists at Johns Hopkins University conducted the study, published this month in JAMA. In a nationally representative sample of Americans, they found that adults with an obese BMI almost always met the criteria for obesity in terms of waist circumstance or body fat percentage, too. The findings suggest that BMI remains an important population-level tool for assessing obesity, the researchers say, even as many people are trying to phase it out.
The researchers analyzed data from the National Health and Nutrition Examination Survey (NHANES), a survey of Americans’ dieting and lifestyle habits regularly run by the Centers for Disease Control and Prevention. As part of the NHANES, some people are given more extensive examinations, which include tests measuring their body fat or waist circumstance.
The researchers looked at the most recent NHANES data (2017-2018) that included people who received these other tests in addition to having their BMI checked. Obesity is typically defined as having a BMI 30 and over (27 for people of Asian descent). But it can also be defined by having a body fat percentage of 25% for men and 35% for women, or a waist circumstance of 40 inches for men and 35 inches for women.
More than 98% of people who were considered obese using BMI alone also fit the bill when either waist circumstance or body fat percentage were taken into account, the researchers found.
“Although certain patient populations (eg, athletes) may warrant further evaluation, our results suggest that these individuals make up a very small portion of the population,” the researchers wrote.
The findings are especially relevant given recent developments in the field of obesity medicine. Earlier this January, a large group of experts called