The largest association of doctors in the US has voted to change its definition of obesity, in a move that could catalyze major changes in insurance coverage, research funding, and public perception of the condition.

In a vote held yesterday by the American Medical Association (AMA) at their annual conference, association delegates agreed that obesity — primarily characterized by a body mass index above 30 — ought to be treated as "a disease, requiring a range of medical interventions." Research increasingly indicates, as the AMA noted, that obesity is a complex condition whose causative factors — like genetics or environment — are often beyond an individual's control. Previously, the AMA and other medical organizations had all defined obesity as a "major public health problem."

"Obesity is a driver of much suffering, ill health, and earlier mortality."

While this new definition isn't legally binding, the AMA's vast influence means that it might very well transform how physicians, legislators and insurance companies address weight loss among those deemed obese. Doctors may be more likely to counsel obese patients on weight loss options, and surgical procedures to promote weight loss, like lap band or gastric bypass, might be covered more comprehensively by health insurance companies. The decision could also see more research dollars allocated to novel pharmaceutical or surgical options.

"[Obesity] is a driver of much suffering, ill health and earlier mortality, and people affected are too often subject to enormous societal stigma and discrimination," said Theodore Kyle, advocacy chair of The Obesity Society, in a statement applauding the decision. "This vital recognition of obesity as a disease can help to ensure more resources are dedicated to needed research, prevention and treatment."

Promote an over-reliance on medication and surgery

But the AMA decision isn't without controversy. In fact, Tuesday's vote diverges from earlier advice by an AMA panel, whose members warned that classifying obesity as a disease threatened to promote an over-reliance on medication and surgery, rather than lifestyle interventions. That panel also noted that the BMI, which is the key metric to determine obesity, carries significant flaws. Most notably, plenty of people with a BMI above 30 are, in fact, perfectly healthy. "Given the existing limitations of BMI to diagnose obesity in clinical practice, it is unclear that recognizing obesity as a disease, as opposed to a ‘condition' or ‘disorder,' will result in improved health outcomes," the panel noted earlier this year.