There is something that I learned about the metabolism while researching diets and fitness that I haven't seen on the internet very much. Many people have tried a no or low fat diet and been unsuccessful. Some of them have even managed to gain fat. How is this done? Well, the little known fact about this kind of diet (or your body in general) is that the human body can create fat from carbohydrates or proteins.
That's right, even if you don't eat fat, your body can still produce and store fat cells.
Reducing the amount of fat you eat can work as an overall diet plan. The theory to it is that since fat is rated at 9 calories per gram, and carbs and proteins are rated at 4 calories per gram, you can fill yourself up and stay low on the calories if you avoid fatty foods. It can work if done properly. You should note that living on a no-fat (0 grams) diet is somewhat unhealthy and some of the better fats (omegas, etc) should be eaten to remain in good overall health.
A low-fat diet is one of the more sound diet plans because although the body can still produce and store fat, it actually takes 40% of the energy to convert carbs and proteins into fat (energy which is created by using/burning those carbs and proteins). The main problem with a low-fat diet, however, is that people tend to cut down too far and end up with a diet they cannot maintain as a lifestyle.