Misleading metrics

Body mass index or BMI, possibly the most commonly used metric to indicate “weight” and its effect on overall health, is now being considered a “highly misleading” clinical measure, according to the American Medical Association in its “Science and public health, 2023” report. BMI, a measure of body fat based on height and weight, though is still widely used by medical practitioners and associations in India, with national surveys being conducted on the regular.

The report states that external factors such as lifestyle issues, gender, ethnicities, medically significant familialdetermined mortality effectors, duration of time one spends in certain BMI categories and the expected accumulation of fat with ageing are likely to significantly affect interpretation of BMI data, particularly in regard to morbidity and mortality rates.

“Parameters along with BMI such as the waist-hip ratio, amount of visceral fat, impact of lifestyle diseases on quality of life, considered along with BMI, are a better predictor of health, rather than just calculating height and weight,” says Dr Raj Palaniappan, director and lead surgeon, Institute of Bariatrics, Apollo Hospitals.

“Recent guidelines passed by the International Federation for Surgery of Obesity and International Diabetes Federation (IDF) have also agreed upon the non-viability of BMI. The Indian Association of Bariatric Surgeons has also sent a memo on this to all governments across the world, including India. ”

Endocrinologist Dr N K Narayanan says one of the major drawbacks of BMI is that it takes into account both muscle and fat mass with no clear differentiation between the two. “A heavyweight champion for example might have a BMI which would be considered overweight. But he would not be prone to diseases as it is mostly muscle mass that is taken into account, whereas a person whoseBMI is higher due to increased fat mass, might be prone to lifestyle diseases.

Someone with type 2 diabetes, who is also obese, if they lose around 15% of their current weight, there is a high possibility of going into diabetes remission,” says Dr Narayanan. “Waist to hip ratio can warn of obesity and cardiovascular disease. ”