Many diseases are differentiated by primary and secondary causes. If you study diseases long enough, you start to see patterns that a lot of them are really tightly interlinked.What if a another disease caused or I should say heavily contributed? Like type 1 diabetes or Hashimoto's? Not sure I that is spelled right.
Of course, then the vagueness comes about again - what is a symptom and what is a secondary disease? Is my neovascular glaucoma a secondary disease, or is it just a symptom of diabetes? Or both?
First off, finding someone who is healthy AND obese is going to be exceedingly rare. Not saying impossible; but if you are 20+ pounds over the top weight for your height then all kinds of risk factors go up. You can feel fine and think you are OK and have no overt symptoms - but a lot of diabetics walking around with blood sugar at 300 don't show any overt symptoms either until they go and get a test and the Dr. goes, "Oh sh1t!"I guess it comes down to many factors. If you get fat next week it doesn't mean you get diabetes, high blood pressure thyroid problems etc etc. If you keep being fat for 10 years you'd probably do damage to your body but it's highly individual just like smoking. Some people get cancer without smoking some just don't get cancer even when smoking a package a day. I think this diseased state at least in my opinion should be based on if this person has developed any signs of damage to the body because obese people can still walk around with a better blood pressure than a guy that's working out and living healthy even if the chances of that happening would greatly decrease.
And diseases often have many factors/underlying causes/possibilities. Again, I use lung cancer because we don't seem to have much issue with re-victimizing smokers and holding them accountable for their lung cancer (nor should we) - but smoking is one potential cause, it is not the result.
In the same way, over eating is just about the only cause of primary obesity (you could say under-exercising or whatever; I know there are shades of gray) - but it is not the result. Obesity is the result, the disease. I don't care if you have secondary diseases or symptoms from obesity or not. If you have normal blood pressure and normal cholesterol, but you carry 100 pounds of fat on your 250 pound body - things are broken. Your fat cells are endocrine sites, and even if you are devoid of symptoms, you will have elevated leptin, reduced adiponectin, some form of insulin resistance (even if it is very minor), reduced dopamine receptor density, etc. Getting fat itself messes all these things up and perpetuates the cycle.
Of course, I guess to play devil's advocate a little - I guess someone walking around with low testosterone who feels fine may not be viewed as "diseased" either....