Well, I'm 13 and I have a diet. But this is not a diet to lose wait! (surprised?)
People think that diets are all about losing wiet, but you can have a diet that will just make you healthyer. i eat just the right amount of things and ristrict myself to junkfood. I only eat about 3 or 4 snack cakes or anything like that a day. I try to keep low on sodium and just a few days ago, when I went to the doctor to get checked for camp, my doctor said that I was just the right wieght for my hieght and my BMI was normal as normal could be.
I don't know any sights that can tell you exactly what you should eat each day, but if you stick to that, then you should be good and healthy on your path to adulthood.
You should eat about 5 servings of fruit and veggies every day. (a serving isn't that big. in fact many children make the mistake of thinking that a bowl full of cereal is a serving, when in fact a serving is only about 3/4 of a cup)
You should eat about 2 servings of meat and 2, 8 oz. glasses of milk. (or other dairy product)
You should eat a lot of things that will give you fiber and grain. You should eat about 10-11 servings of bread and grains a day. ( for ex. a sandwich is 2 servings because it has 2 slices. A bowl full of cereal also has about 2 servings. That's already 4 servings!)
Also remember to exercise and play. try doing something you enjoy like jumping rope or hula hooping. You can even play sports as a form of exercise. You shouldn't start lifting wieghts or anything untill you are at least 12 years old.
I also know that tea (of any kind) gives lots of antioxedents. This helps prevent cancer and gives you lots of vitamens. Green tea is the most popular, but herbal tea has (with my opinion) the best flavor.
Well, good luck on your trip to getting healthy!!!