Re-evaluating indiscriminate use of BMI to make conclusions on health

General Studies Paper 2

Introduction

• India is said to be among the least obese countries in the world, with an average Body Mass Index (BMI) of less than 22.BMI –the ubiquitous tool believed to measure fat and fitness – would classify most Indians as healthy. But more Indians than ever are at risk of type 2 diabetes, high blood pressure and cholesterol levels. Obesity, experts warn, isa “ticking time bomb”.

BMI

• The paradox is built within the tool of choice – the BMI, a simple calculation that divides an individual’s weight in kilograms by the square of their height in meters.
• The most-repeated myths about fitness are “the lower the BMI, the healthier you are…or that obesity happens only when you’re not eating well or exercising regularly”. Both claims are misleading and untrue.
• BMI is one method of tracking your weight and identifying potential weight-related problems.  Like a Rapid Antigen Test for COVID-19, it may help screen for chronic health conditions without promising the accuracy of an RT-PCR test.

A product of bias

• Some 200 years ago, a Belgian astronomer and statistician Adolphe Jacques Queenlet wanted to study humans and develop ‘social laws’, like the laws of physics.
• He pored through available datasets to find the ‘average man’, using the height and weight of Caucasian, middle-aged men from France and Scotland.
• The Queletet’s Index, the first iteration of the BMI, helped identify a type of perfection and intended for it to be a population-level tool only, cautioning its use on individuals.

A complex science

• Mounting evidence since has led people to reconsider the logic of BMI.
• For one, BMI doesn’t-understand weight entirely, is unable to distinguish between muscle mass and body fat.
• Muscle and bone are denser than fat and thus weigh more; explaining why people with larger body frames (like athletes) have a higher BMI and older adults (who lose muscle mass) tend to rank lower.
• BMI clumsily threads the needle between obesity and mortality, mistaking correlation for causation.
• People who are obese have a high BMI, but it is not necessarily true that a high BMI implies obesity.
• The science around ‘fat’ is constantly evolving. It is known that excess body fat increases the risk of non-communicable diseases, such as type 2 diabetes, heart conditions and 13 types of cancers.
• An analysis in Science journal, however, found ‘obese’ people (with a BMI of 30 or more) carried a lower cardiovascular risk, and those in the ‘normal’ range were metabolically unhealthy and had a higher mortality risk – what it called the “obesity mortality paradox”.

More findings

• Research has found at least 59different types of obesity, making one measure of ‘body fat’ impractical.
• The measure also relies only on self-reported weight and height, disregarding other influences such as bone density, muscularity, sex, age, genetic differences, per a-study in the International Journal of Obesity.
• Social factors such as poverty and educational so influence weight and obesity.
• Body fat also varies across ethnic and racial groups. Asian Indians, for instance, suffer from the Y-Y paradox, i.e at the same BMI, we have more visceral fat — the fat inside the stomach — than Europeans do.
• Since Indians are prone to abdominal obesity, they are at higher risk of type 2 diabetes and heart diseases, studies show.
• WHO notes that BMI underestimates health risks for or South Asians, and the optimal health for Indians would then be a low BMI.

Conclusion

• The American Medical Association (AMA) on June 14 this year accepted that BMI was an imperfect way to measure body fat for it does not account for differences across race/ethnic groups, sexes, genders, age-span and had caused historical harm.
• AMA’s decision echoed a longstanding consensus among experts and activists that BMI is flawed, discriminatory and takes away targeted attention from health crises such as the alarming prevalence’ of non-communicable diseases.