My guess is -- correct me if I'm wrong -- it's because you're not a doctor or researcher who works in any of these areas (nutrition, obesity, addiction), and haven't read much research on the intersection of these topics.
> I think obese people fit the definition of addicts.
I'm curious how you have arrived at this conclusion.
I'm an engineer. I want to understand stuff. Obesity is a perspective that I thin can give a ton of insight about human nature, society, evolution, progress, globalization, advertisement, medias, etc.
As for the definition, feel free to pull the definition from anywhere and see if there are any contradictions when applied to obese people.
http://www.asam.org/quality-practice/definition-of-addiction