An international committee of scientists has proposed changes to how obesity is defined and diagnosed. The goal is to provide a more nuanced and objective way to assess body composition by adding more metrics, such as waist circumference, to the criteria.

For years, the method doctors have used to determine whether a person is obese is to calculate their body mass index (BMI). BMI is a quick and cheap estimate based on weight and height.

But the committee concluded that BMI did not provide adequate information about an individual's health and that relying solely on BMI could lead to misdiagnosis.

Dr. Robert Kushner, an endocrinologist at Northwestern University and a member of the Lancet Committee on Diabetes and Endocrinology, explained that current measures of obesity based on body mass index can either overestimate or underestimate a person's body fat content.

"If obesity is defined solely by BMI, approximately 40 percent of adults in the United States are obese," Kushner said. But do these millions of Americans suffer from this disease? Do they all need treatment? Kushner said the committee's purpose was to clear up the confusion.

Some are stocky and muscular. When they step on the scale, their weight may put them in the obese category due to muscle mass. But these people may be healthy.

On the other hand, some people have very low muscle mass but carry excess weight around their organs. Their body mass index may be within the normal range, but their belly fat levels may put them at risk for metabolic disease.

"What's new is that we're trying to define obesity by excess body fat, which is what obesity really is," Kushner said.

The committee recommends that excess body fat should be identified by measuring a person's waist circumference, waist-to-hip ratio or waist-to-height ratio. Another option is to measure body fat directly through screening, such as a DEXA scan (if that option is available and affordable).

"We are not abandoning body mass index, and we are now recommending that individuals take another measurement that provides a more direct estimate of body fat," Kushner said.

Bottom line: The new measures focus on the amount of fat around people's waists.

"Fat in the belly can cause inflammation throughout the body, which can lead to other metabolic problems, such as increased blood sugar, increased blood pressure and increased fat in the blood," Kushner explains. This could set the stage for metabolic diseases including diabetes and heart disease. Base.

In addition, the committee recommended two new obesity categories based on objective measures of the disease. The first category, called "clinical obesity," applies to people who already have chronic conditions related to obesity. The second category, called "preclinical obesity," means a person is at higher risk of developing health conditions due to body fat levels.

Dr Francesco Rubino of King's College London, chair of the committee, said: "Our reformulation acknowledges the nuanced reality of obesity and allows for personalized care."

The committee is composed of 56 experts in the fields of nutrition, endocrinology, internal medicine and public health. Their report was published in Magazine Lancet Diabetes and Endocrinology.

The report comes as obesity rates rise significantly across the world. The World Health Organization estimates that more than 1 billion people are obese, and the World Obesity Federation estimates that the economic impact of obesity will exceed $4 trillion by 2035.

This story was edited by Jane Greenhalgh