For years, body mass index (BMI) has been the standard for diagnosing obesity. However, a new report by the Lancet Global Commission calls for a change in how we assess it. The study argues that BMI misses important health factors and advocates a more comprehensive approach.
Metrics for BMI
Supported by more than 75 medical organizations, including the All India Association for the Advancement of Obesity Research (AIAARO), the report calls for additional measures such as waist circumference and waist-to-hip ratio to better assess the health risks associated with with obesity.
“Waist circumference is a measure of the narrowest part of the waist, often above the belly button, and is used to assess abdominal fat, which is associated with health risks such as heart disease and diabetes,” says fitness expert Aman Jain. He goes on to explain that waist-to-hip ratio (WHR) divides waist circumference by hip circumference to estimate fat distribution. In addition, tools such as DEXA scans allow doctors to directly measure body fat, offering a more accurate assessment of obesity.
Why BMI needs rethinking
BMI, which is calculated by dividing weight (in kilograms) by height (in square meters), is favored for its simplicity. However, the method has obvious limitations. It does not take into account muscle mass, fat distribution or ethnicity, meaning that two people with the same BMI may have different health risks.
“Other factors such as muscle mass, age, gender and presence of co-morbidities should also be considered when defining obesity in the general population or in obese patients,” says Dr Bhushan Bhole, senior consultant, PSRI Delhi.
Also, the main drawback of BMI is that it does not distinguish between subcutaneous fat (just under the skin) and visceral fat (around the internal organs). The latter is much more dangerous, associated with a greater risk of heart disease, diabetes and other serious diseases.
“BMI has long been used as a simple indicator, but it does not tell the whole story of a person’s health. By adding measures such as waist circumference and introducing categories such as clinical and non-clinical obesity, we can better tailor care to each individual’s needs,” says Dr R. R. Dutta, head of internal medicine at Paras Health in Gurugram.
To top it all off, Dr Nikhil Agnihotri, senior consultant at Aakash Super Specialty Hospital in Delhi, emphasizes the need to go beyond BMI. He goes on to explain that more sophisticated methods can be used. “We can use advanced imaging techniques like CT to directly assess visceral fat, or during surgery we can directly observe and measure visceral fat,” he mentions.
