Fat Loss 4 Idiots is basically a diet plan that tells you to eat the right foods at the right intervals each day. It is based on calorie shifting where you change your calories intake every day, and thus confuses your body into burning off more calories.
At the start of the Fat Loss 4 Idiots handbook, you are presented with 2 weight loss programs and you choose which you want to follow. One is the Diet Generator which is for people who wants to lose weight quickly. The other is a more casual approach, in which you follow 10 weight loss rules and not a fixed diet.