Theres no such thing as fattening and un fattening foods.
The reason why some foods have the reputation of being fattening is because there may be many calories in it or there may be a lot of fat in it. The only way you can get "fat" is from eating too much food (aka eating more calories than you burn), not by avoiding "fattening" foods.
Healthy foods are foods that are dense in nutrients and may or may not be dense in calories. Healthy foods are things like vegetables, fruit, nuts, seeds, whole grain breads, lean meat, low fat dairy products, etc.
The key to all diet rules is moderation. You can eat anything you want as long as you dont over do it. Good Luck =]