It should be, "You want to reduce the amount of fat on your body?" The answer is not how much you eat or what you eat. It is the relationship between how much work your body does for a given action and how affective it is at utilizing calories from the food you eat.
If you eat a lot of food and burn a lot of calories and your body is not very good at turning the food you eat into energy, you will be thin. If the first are the same and your body is good at utilizing the food you eat, you will be muscular.
Manipulate those factors and you will find a simple formula that will determine food to work to weight to muscle.
My body just happens to do no work, consume lots of food, and is great at converting it to be used.