By Clinical Research News Staff 

April 2, 2025 | Body Mass Index (BMI) is a long-used method to measure body fat with the formula kg/m² (or lbs/in² x 703 for imperial measurements). While it is a noninvasive and inexpensive way to measure body fat, there are arguments that BMI is inaccurate because it does not include other factors such as fat distribution, muscle mass, and metabolic health. The use of BMI has even led to a negative impact on clinical trials and caused misunderstandings about weight loss drugs. 

The Lancet Diabetes & Endocrinology recently published new guidelines (DOI: https://doi.org/10.1016/S2213-8587(24)00316-4) that included a proposal to replace the BMI system and aimed to establish new objective criteria that better align with obesity as a disease. The proposal separated obesity into two categories—preclinical and clinical. 

“Preclinical obesity is the new category to encompass anyone with high adiposity, or body fat, levels,” explains Antoine Robiliard, VP of Withings Health Solutions who was not an author of the paper. “Clinical obesity refers to someone who has high body fat and is having other organ dysfunction or impairment as a result of their body fat.” 

To validate the new obesity guidelines, Withings conducted an analysis of 3.4 million Withings scale users between the ages 20-79. They found that about 38% of people were classified as overweight or obese under traditional BMI guidelines. However, under the newly proposed definition, they are not classified as obese or preclinically obese. In fact, the analysis found that the 38% of users classified as overweight under BMI guidelines actually had healthy body fat levels and would be classified as healthy using body composition. 

“When BMI is used, there is no distinction between someone who has high muscle mass and is metabolically quite healthy, and someone who is at risk of disease through their visceral fat level,” says Robiliard. Visceral fat refers to the fat that surrounds the organs, and it is linked to illnesses such as cardiovascular disease and fatty liver disease. By measuring visceral fat—and other components—through body composition methods, a more accurate reading of an individual’s overall health can be provided. 

Withings Health Solutions, a division of Withings, has developed Body Pro 2, a scale that uses bioelectrical impedance analysis (BIA), a harmless and undetectable electrical current, throughout the body and takes in the amount of resistance it encounters when it reaches muscle or fat. The scale then uses formulas to measure body composition. This results in a more accurate assessment of a person’s body fat and health risks, thus allowing patients more tailored, evidence-based treatment plans. Body Pro 2 is also useful for tracking progress and monitoring trends. Not only can it be used at home, but clinicians and researchers can also use Body Pro 2 as a tool for engaging with patients and tracking their health.  

Moving beyond BMI can align obesity with other chronic diseases and alleviate the weight stigma, which is still a “massive issue that prevents many people from going to their medical appointments,” according to Robiliard. Focusing on body composition instead of just body fat can allow improved patient outcomes and better treatment methods.   

With the release of the scale, the team strives to continue highlighting the benefits of body composition over traditional BMI methods. “We expect that leveraging body composition will soon be the new standard in the healthcare industry, particularly in GLP-1 medication-based programs, to ensure safer weight loss.”