More than any other age group, teens need a lot of energy. Energy comes from calories and on a daily basis, teenage boys need about 2,500 to 3,000; teenage girls need about 2,200 calories. The good news is that most teens have no problem acquiring them. But parents should note how the calories are being consumed. A bag of potato chips with a 44-ounce Big Gulp will add calories quickly, but fatty snacks and sugary soda drinks contain very little nutrients. So obviously this typical teenage meal will contribute only to weight gain, and not to your teen's overall health.

Calcium and iron are two essential nutrients for teens because they help build strong bones and reduce the risk of osteoporosis. Teen athletes especially need calcium for maintaining muscle tissue and a regular heart beat. Iron helps red blood cells transport oxygen throughout the body, giving kids energy.

Signs of weakness and fatigue usually translate to a shortage of iron in the diet. Teenage girls are especially concerned about body image, so they tend to avoid fatty items like dairy products. Studies say they are hurting themselves in the long run by doing this. They also mention that teen girls are missing out on good fats like omega-3 and monounsaturated fats, which are good for healthy skin, hair, and the immune system. They have also been shown to reduce depression.