Are we thinking about obesity all wrong?

Experts are rushing to redefine obesity amid soaring demand for new weight loss drugs.

- Iulia Belluz

"Obesity is a disease," Oprah Winfrey declared after disclosing her weight loss with an Ozempic-like drug. "It's a brain disease," a prominent obesity doctor explained on a "60 Minutes" episode about the drugs. "Obesity is disease" even has its own discover page on TikTok.

The American Medical Association and the World Health Organization share that view, but whether obesity should be considered a disease has been referred to by health experts as "one of the most polarizing topics in modern medicine". Even Jens Jul Holst, a discoverer of the hormone that drugs like Ozempic mimic, told me he isn't sure what to call obesity. "Whether it's a disease in its own right is a very difficult question," he said. Finally, this dispute is coming to a head amid soaring demand for new weight loss medicines, as expert groups around the world rush to define what it means to have obesity.

At the heart of the debate: the medical community has never provided a precise definition for obesity as a disease. It's typically understood as an excess of body fat, using body mass index, or BMI, to gauge who has too much. But BMI - a person's weight divided by the square of their height - was never meant to be used as a diagnostic tool and can't determine whether someone is healthy or sick. And there's no consensus on the signs and symptoms that make obesity an illness the way high blood sugar levels are used to diagnose Type 2 diabetes, or chest pain and irregular imaging to tell if someone has heart disease.