Simon...
One must think the situation through.....Fat Chicks are okay....what you lose on the food bill is offset by the fact you have no entertainment expenses to speak of. Certainly, you will not be taking her out often and a night in front of the TV with a six pack of beer and a large bag of Crisps should keep her entertained.
Remember, fat girls will appreciate what you are doing for them and wash your clothes for you as well as do the cooking.
Don't discount your options prematurely.