Perspective: Obesity is not a disease

The misguided urge to pathologize this condition reflects society's failure to come to terms with the need for prevention, says D. L. Katz.

Doctors are historically ill-prepared to address the problem of obesity — with a tendency either to ignore it, or to ineffectually wag an admonishing finger1,2,3. To focus physicians' attention on this prevalent health issue, the American Medical Association (AMA) recently declared obesity to be a disease. This well-intentioned move by the AMA is misguided in that it implies that tens of millions of people must now have bodies or minds, or both, that are not working properly. Even seemingly healthy, but heavy, people — adults and children alike — are now, by definition, diseased4. Imposing such a status has broad ramifications for society and requires careful reflection.

The standard measure of obesity is body-mass index (BMI), which is roughly speaking the ratio of weight to height. For adults, a BMI greater than 30 is associated with increased risk of illness, disability and death. However, a risk factor is not a disease, because each can occur independently of the other.

Obesity is an important contributor to the prevailing burden of chronic disease, lying on the causal pathway to much of what plagues modern society and its people — heart disease and diabetes to name two of the most serious. However, not only can these diseases develop in the absence of obesity, but not everyone with a high BMI develops any such condition.

“The categorization of obesity as a disease could have a pernicious influence on efforts to remedy the condition.”

The categorization of obesity as a disease could have a pernicious influence on efforts to remedy the problem at its true origins. The treatment of diseases customarily involves drugs, medical technology, clinic visits and surgical procedures. If obesity is a disease, the therapeutic advances on which its management depends presumably reside in these domains.

Heavy costs

The disease approach would impose substantial costs. Obesity affects many tens of millions of adults and children in the United States alone5. If we were now to conclude that all these individuals warrant disease treatment, the collective need for drugs and bariatric surgery would be staggering. That would mean not only a huge financial outlay, but the imposition of a vast array of side effects on the overweight population. Even the best of drugs are prone to side effects, and to date, weight management has been forced to rely on anything but the best of drugs6. The long-term effects of bariatric surgery are still highly uncertain as well — particularly for ever younger candidates. Even if surgery proves sustainably effective, the need to rely on the rearrangement of natural gastrointestinal anatomy as an alternative to better use of feet and forks seems a societal travesty7.

The consequences of labelling obesity a disease seem to be a price the medical profession is willing to pay to legitimize the condition. It may also be an attempt to own it, and the profits that come with treating it.

Our bodies, physiologies and genes are the same as they ever were. What has changed while obesity has gone from rare to pandemic is not within, but all around us. We are drowning in calories engineered to be irresistible8. We are awash in labour-saving technologies and a societal mindset that urges us to use all that we invent9.


Like breathing air, our capacity to get fat is part of normal physiology. The dividing line between normal and abnormal fat accumulation has nothing to do with fat accumulation per se, but rather whether or not those energy reserves, a fundamental survival strategy of omnivorous and carnivorous animals, are ever drawn down. In our ancestral context, they were; in our modern context, they never are.

We don't wait for people to drown and devote our focus to resuscitation. Instead, we do everything we can to prevent drowning in the first place: we erect fences around swimming pools, station lifeguards at beaches, offer swimming lessons, and keep a close eye on one another at the water's edge. People still drown, so we need medical intervention as well. But that is a last resort, far less good than prevention, and applied far less commonly. There is an analogous array of approaches to obesity prevention and control. These include environmental reforms, such as making stairs, pavements and bike lanes more readily available, and altering food service settings to encourage the more healthy choices; social reforms, such as making physical activity programming a standard aspect of every work and school day; policy reforms, such as regulation of both food formulations and food marketing; and skill-building, including teaching adults and children how to identify more nutritious foods and how to cook.

Obesity warrants medical as well as cultural legitimacy and respect, but needs not be a disease to earn them. Calling obesity a disease contradicts the functioning of our bodies, and implies a blame residing there. But the blame for hyperendemic obesity, and its best remediation, resides not within bodies that work as they ever did, but all around, with the collective actions of the body politic.


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Correspondence to D. L. Katz.

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Katz, D. Perspective: Obesity is not a disease. Nature 508, S57 (2014).

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