Imagine you’re obese. Would you describe yourself as “diseased”? The American Medical Association would. In 2013, it decided obesity was a disease. This was mainly, it must be said, for pragmatic reasons, to “help change the way the medical community tackles this complex issue.”
Or, as somebody far more cynical than I might say, in order to give doctors something else they could bill health insurers for.
Not everyone was convinced. Obesity, critics argued, lacks a tightly defined set of symptoms (you don’t get a fever or break out in spots) and specific functional impairments. Obesity may be one of the causes of diseases such as diabetes, but surely calling it a disease in itself was drawing a long bow, they claimed.
This is more than a semantic debate; it involves stigma, blame, drugs and lots and lots of money.
The Disease Solar System
I find it helpful to think of diseases as being organized as a kind of solar system, in a series of concentric circles. At the very heart of the disease solar system are “paradigm diseases,” such as Ebola and measles. They have physical effects caused by a single vector (an agent that carries and transmits the disease), they’re communicable and have a well-defined set of signs and symptoms.
A little further out from the center, we might find depression, which has specific diagnostic criteria, appears to be treatable by common drugs such as anti-inflammatories, but is not really communicable.
Far from the center, we might see, say, cerebral palsy. Is it a disease at all, or a condition? And then there are “diseases” such as irritable bowel syndrome and repetitive strain injury, which whizz in and out of our disease solar system like haywire comets.
Diseases share a number of characteristics, but not all diseases have all those characteristics. They follow a pattern that the philosopher Wittgenstein called “family resemblances.”
Obesity certainly has some disease characteristics. It has a clear diagnostic criterion—a BMI of 30 or more. It has a known set of common symptoms (high blood fats, for instance, and poor blood sugar regulation).
Obesity may even be communicable through social networks. One study found that a person’s chances of becoming obese increased by 57 percent if they had a friend who became obese.
