For those on a tight food budget, it's best not to blow the money on fast food (or on eating out at all). Shop smart, and carry your food with you. (Gladware is a super investment, and only about two bucks for a pack of 5 containers with lids).
On $180/month, you can easily pick yourself up a healthy array of things like tuna, chicken breast, ground beef and/or turkey, oats, eggs, yams, whatever fibrous green veggies (or fruits, if you eat them) are in season and/or on sale, brown rice, wheat bread, pasta, etc., and even have a little room for some extras (condiments, spices, coffee/tea, occasional treats, etc).
Just remember to keep an eye out for sales, shop around and get familiar with which stores offer the best prices on certain items, buy store brand when you can, and buy in bulk if possible. I do a lot of running around when I grocery shop, but it saves me a lot of cash in the long-run. For example, I buy organic rolled oats for 0.69/lb. from the bulk bins in a local health food store (but I refuse to buy their double-price produce and meat). I only buy bagged salad mixes when they're on sale or buy-one-get-one free (else, I'll go wherever lettuce and fixings are cheapest). I often go to local farmers' markets or produce stands. WalMart has fantastic meat prices. You get the picture.
Those dollars can go farther than you'd think, if you plan carefully!