You guys are overcomplicating this. I'm not suggesting canabilism. The average fatass stores enough calories to last them for months, maybe a year. Just don't feed them at all. Give them a daily vitimin tablet, water, and they'll be fine.
Toss a few of the slowest and lasiest into the ovens to produce heat and electricity (as fat makes a fine, long-burning fuel), and the camps will be more or less self sufficient.