I worked in restaurants (large family style restaurants, not fast-food) for almost ten years when I was younger and I used to eat whatever I wanted. Typical daily caloric intake was usually around 4000 calories or more, and I never gained weight. My metabolism slowed down drastically when I was in my 20's however, and I started packing on the pounds.
I went on a diet last fall and lost 30 lbs in 3 months (from 245 to 215 lbs), but I got lazy over the holidays and the winter and I've gained back 20 of the pounds I lost. I'm back on the diet again and plan to get down to 200 lbs even (I'm 6'1") by summer. Currently I only eat food one day a week (Sunday), and then I eat whatever I want, as much as I want, but I don't stuff myself. The other 6 days a week I don't eat, I only drink. Homemade protein shake for breakfast, Slimfast and fruit juice for lunch, and watered down cream of chicken soup for supper. Every day. I still get around 1500 calories a day, and the main point is to burn off more calories than I take in. Once I get down to 200 lbs this summer, I'll still have one or two liquid meals a day, and then one or two small solid meals a day of whatever I want. The point is not to limit what kinds of food I eat, but how much.
-Keith