It's ALWAYS genetics. This is a fun story about how obesity is caused by the choices you make and is in no way pre-determined.  At my work I spotted a wild hambeast, not uncommon, there are a lot of Texan tourists where I work. But this ham was definitely items one if the larger ones, and it was with a normal human. These two were quite obviously siblings with the same facial features but the hambeast had ballooned most of the resemblance into oblivion.  I'm a fairly vocal shitlord, so when I saw this magnificent sight at my work this weekend, I was quite loudly exclaiming "it's ALLLL GENTICS" and continued to go off about how the choices we make matter. There was nothing any of my fatty coworkers could say.