We all know that burgers and fries aren't the most nutritious foods in the world, but none of us is about to give them up. That's okay. No food is bad as long as you don't overdo it. If you do eat a lot of junk food one day, eat lots of green leafy vegetables, lean meat or poultry, and fruit the following day. And remember these tips:
Pump more iron into your diet. An adequate iron supply is vital once you've started menstruating because monthly blood loss can lead to iron deficiency. Not getting enough iron can also leave you tired and irritable and make it hard for you to concentrate in school. Eventually, you may develop anemia, a shortage of red blood cells. To increase your iron level, eat iron-rich foods like lean red meat, fish, poultry and iron-fortified breads and cereals every day. Although spinach, peas, beans and other vegetables also contain iron, your body doesn't use the iron from them as well unless you also eat a lot of foods high in Vitamin C, like peppers, tomatoes, citrus fruits, cabbage and potatoes.

Bone up on calcium. Because your bones grow to their full strength and density by the time you're 20, your teen years are your last chance to ensure that you'll have strong bones when you're a grandmother. Girls particularly need to build strong bones now because women are more at risk than men for developing osteoporosis, a condition that causes older people's spines to curve and their bones to break easily.

Calcium, the main mineral in bones, provides them with strength and density. Experts agree that you should include 1,200 to 1,500 milligrams of calcium in your daily diet. Five glasses of low-fat milk is all it takes. While milk is the best calcium source, it's certainly not the only one. Low-fat cheese, low-fat yogurt, and sardines or salmon with the soft bones also contain significant amounts of calcium. If you're lactose-intolerant, drink lactose-free milk or try lactase pills that can help you digest dairy products.