The Right Way to Tell Obesity Is Key to Our Well-being

BMI provided a shaky foundation for understanding obesity and related health risks. A shift to more accurate anthropometric measures must now be accompanied by a composite and committed policy response

- K Srinath Reddy

Over the past half-century, obesity has emerged as a vexing global health challenge—both because of the several adverse health effects and struggles with understanding the nature of a body's "fatness." Even as the prevalence of obesity was rising rapidly across the world, health professionals were unclear as to whether obesity should be labeled as a disease in itself or merely as a risk factor for other diseases. A distinction was notionally drawn between "overweight" and "obesity." Recognition of amplified health risks posed by visceral or abdominal obesity, as distinct from the risk posed by general obesity, brought a new dimension to debates around obesity as an omnibus term.

As scientists sought to define obesity through quantifiable anthropometric measures, debates raged over whether the problem arose from personal behaviors of eating and exercise or from commercial forces that propelled changes in patterns of food consumption through their manufacturing and marketing practices. Attributing obesity to an individual's gluttony or indolence led to body shaming and social discrimination. And now, with powerful new weight-loss drugs emerging recently, calls to treat obesity as a disease have become louder.

Amidst these debates, the Body Mass Index (BMI), proposed by Belgian mathematician Adolphe Quetelet in 1832, became the anthropometric index considered cardinal for obesity identification. BMI is derived by dividing weight (in kilos) by the squared value of height (in meters). In Western populations, a BMI between 25 and 30 was classified as overweight, and values above 30 as obese. "Normal" BMI ranged between 18.5 and 25, while BMI below 18.5 was classified as being underweight. The World Health Organization (WHO) recommended these standards for all populations.