A group of experts from around the world are proposing an alternative way of defining clinical obesity, eschewing the commonly referenced body max index (BMI) and instead approaching the condition similarly to chronic illnesses to improve decision making when it comes therapies and public health strategies.
The Lancet Diabetes & Endocrinology Commission asserted in a paper published this week that “current BMI-based measures of obesity can both underestimate and overestimate adiposity and provide inadequate information about health at the individual level, which undermines medically-sound approaches to health care and policy.”
According to a September 2024 data brief from the Centers for Disease Control and Prevention (CDC), 40.3 percent of U.S. adults were considered obese between August 2021 and August 2023.
In the U.S., adult obesity is defined as having a BMI greater than 30. BMI is calculated by dividing weight over height without accounting for body composition.
The Lancet Commission is comprised of 58 experts with multiple medical specialties and individuals who have lived experiences with obesity.
For their definition, the group focused on adiposity, the amount of fat stored in the body, and how it affected organs and tissue.
“We define clinical obesity as a chronic, systemic illness characterised by alterations in the function of tissues, organs, the entire individual, or a combination thereof, due to excess adiposity,” the commission wrote.
By this proposed definition, a diagnosis of clinical obesity requires one or both criteria: evidence of reduced organ or tissue function due to obesity and substantial age-adjusted limitations of daily activities due to obesity.
Preclinical obesity was defined by the group as a “state of excess adiposity with preserved function of other tissues and organs and a varying, but generally increased, risk of developing clinical obesity and several other non-communicable diseases.”
They recommended that BMI should only be used as a “surrogate measure of health risk at a population level, for epidemiological studies, or for screening purposes, rather than as an individual measure of health.”
Using BMI to define obesity carries “several limitations” according to the commission. Because BMI doesn’t differentiate between lean mass and body fat, some people with normal BMIs may have excess body fat that could put them at increased risk for certain conditions. On the other end, the commission members noted individuals with BMIs that define them as obese may not have excess fat, leading to an overdiagnosis of obesity.
