Maybe it’s already been said, but people tend to think of obesity as being similar in kind to addiction. Well, that’s one component of it.
Having known a morbidly obese person, it seems patently clear to me that it is a disease in that obesity is physiologically global.
Like anorexia, it most often originates in a psychological issue, affecting behaviour, appetite, outlook, social behaviour, and, most importantly, health. The co-morbidities involved in obesity are many, and the origins of the problem are plural.
It’s certainly not as simple as saying that you are what you eat – to the obese, what you eat is a symptom and a cause of the problem.