No prob,I give this a lot of thought too, being as I am skinny and my friend is huge (ever see the movie Nacho Libre?
http://m.toledoblade.com/image/2006/06/16/800x_b1_cCM_z/Movie-review-Nacho-Libre.jpg yeah that's basically me and my friend. XD)
He is huge and while I do think his diet may have something to do with it, I do think genetics have a role. His dad is huge and short, his mom is tall and thin, his older brother takes after his mom(being tall and thin) but him and his sister are short and huge. So I have to wonder how much
genetics have to do with it, but then again some diseases are genetic so maybe obesity could be considered that too. Another thing is metabolism, if your metabolism is out of wack, then it will be really hard for you to lose weight, and (not to get too deep here XD) if you have a hormone imbalance then that will throw your metabolism for a loop, and almost everything these days will effect your hormone levels. Now as to it being a disease, well, a disease can be genetic, and can be the outcome of a lifestyle so yeah, I think it is most likely a disease. Now the problem is, what to do about it? I guess that depends on HOW the person got it, if its genetic, then they'll have to work a lot harder to improve their health, if its a hormone imbalance, figure out the cause and correct it, and if its just diet and exercise then.... that may actually be a simpler fix. And yeah help and knowledge will help if it can get out there but it hasn't, and someone needs to figure out the "how".
Sorry for my block of text too, I have the same problem XD