why are so many homeless people fat?

my last post reminds me of an age old question about homeless people....why are so many of them fat? i'm not talking like a little bit chubby, i'm talking about grotesquely obese. if they are homeless and have no money....how do they get food? more importantly, how do they get so much food that it gets them so crazy fat? i mean, they are (for the most part) walking around the city all day asking us for money. that is certainly a form of exercise, no? i think if i was homeless, with no money and had to beg for food and other stuff....i'd be insanely thin. like, emaciated. but then again, i think being homeless requires being a drunk. that's probably where they get the empty cals.