Obesity: Lancet says focus on fat distribution, not just BMI

The Lancet Diabetes & Endocrinology Commission, a group of 58 leading experts from various medical specialties and countries, on Tuesday proposed a new approach to defining and diagnosing obesity. This approach goes beyond just using Body Mass Index (BMI)—a numerical estimate of a person’s weight relative to their height, traditionally used to determine obesity.

The commission acknowledges that BMI is a helpful screening tool for identifying people who might have obesity but experts suggest it shouldn’t be the sole method. Instead, they recommend confirming obesity by assessing excess body fat and how it’s distributed in the body.

The new approach to diagnosing obesity in an individual may include waist circumference, waist-to-hip ratio, waist-to-height ratio or direct fat measurement, says the report by The Lancet Commission on Clinical Obesity, endorsed by 76 organisations and 58 experts globally.

Additionally, the commission has for the first time also recommended two new diagnostic categories of obesity based on objective measures of illness at the individual level—clinical and preclinical.

While clinical obesity should be seen and managed as a chronic disease associated with ongoing organ dysfunction due to obesity alone, preclinical obesity can be associated with a variable level of health risk, but no ongoing illness, experts have said.

As of now, the World Health Organisation (WHO) defines overweightedness and obesity in adults using BMI alone. Those with a BMI between 25 and 30 kilograms per square metre are considered overweight, while people with a BMI of more than 30 kilograms per square metre are classified as obese.

These BMI cut points are essentially based on health risk escalation beyond a certain BMI. However, over the years, the understanding of obesity has evolved following evidence suggesting that health risks in people with the same BMI may vary with ethnicity and may lead to different decisions on public health action.

For example, individuals of Asian descent are more susceptible to obesity-related health problems at lower BMI values than whites at the same BMI levels. This lower threshold considers the increased risk of non-communicable diseases such as type 2 diabetes and cardiovascular disease among Asians.