I used to be in a situation where, with no kitchen of my own and not even a sink in my living space, I was forced to either use a kitchen I shared with druggies or go to Mc Dicks. Guess what? I didn't get fat because I biked or walked everywhere, even in the 'unsafe' areas, and I didn't eat a bunch of burgers and fries. One may not fill you up, but it does give you the calories you need to keep going. If you're obese you need less since you're already carrying around an energy soruce around your stomach and ass and chins. Of course, this doesn't cover the need to have proper nutrients, which I think is a bigger issue when it comes to poverty and food deserts.