I'm not sure which diet to use.
Kyle (age 17)
At your age, the best diet is to eat a large variety of things but control the portion sizes. One trick is to never eat more of one item than the size of your fist or the palm of your hand in a meal. You can have three or four items but each must be limited in size. For "junk" food, such as chips or cookies, restrict yourself only to the serving size on the bag. for a day.
So I shouldn't really try the Atkins diet or anything like that because of my age? I am trying to build more muscle and have more definition, though if I'm not eating correctly, I feel I'm wasting my time.
The Atkins diet is thought to be good for people who are diabetic, but it hasn't gotten good reviews as a good all-round diet. You can go to "Atkins Diet Review" for a fair description and warnings about the diet. Even though you are done growing externally, you are still development internally for several more years. You don't want a diet that limits the variety of food that you eat at this time -- if ever. Cutting down on sweets, heavily salted food, fried foods, and junk foods will be the best thing for you now and into the future. As Americans we tend to eat too much food and not enough of a variety to get well-balanced meals.
Being a young male, you have the advantage of being able to lose weight quickly and relatively painlessly simply by reducing the amount you eat. Fancy diet plans are not necessary unless you are having a particular problem.
Whatever you eat will not build your muscles, it just gives you the fuel and nutrients needed to build muscles if you exercise properly. The only thing that will actually cause your muscles to grow is exercise.