Hey, can't have you playing alone.
The Dead Broke Method
Begin by getting rid of more or less all your money, only keep enough for rent. Now only buy cheap vegetables and fruit, or go dumpster diving for food that the supermarkets have thrown out. Cook all your food yourself, eating out is expensive. Even better, just eat the food raw, electricity and gas for cooking is expensive to.
You'll get lots of exercise. With no money you won't be able to afford running and maintaining a car, so you will have to walk everywhere. Only take the bus when going far, as that costs money too. Once you've reached your target weight, begin earning some money again...as it's actually not very fun being dead broke.
This is a tried and tested method (by me) and actually works.