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Exercise, food, and fluids

3 bottles of water

It is best not to exercise with a full stomach or you may feel uncomfortable and sick to your stomach. Give yourself 60 – 90 minutes for small meals to digest, and up to four hours for bigger meals (any longer and you will be hungry again!). If you are competing in several athletic events in one day, such as a bunch of tennis matches, it will help to eat small snacks in between events.

Water is the most important nutrient for your body when you exercise. Drink it before, during, and after exercise or sports competitions. You should keep drinking water throughout the next day after heavy exercise.

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Some athletes try to get rid of water weight before a big game or event by sweating in a sauna or using a laxative or diuretic (makes you urinate more). This can actually hurt an athlete's performance and also lead to serious health problems.

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Food as fuel

If you’re playing sports, you have special nutritional needs. Teens who exercise need more food to support both your performance in your activity and your growth. Depending on how active you are, you may need anywhere from 2,000 to 5,000 total calories per day to meet your energy needs. But increased calories are only needed for those who play hard and for a long time. Eating too many calories while only doing light exercise could result in weight gain.

So what happens if you play sports and don't eat enough? Well, your body may be sluggish. Instead of building muscle, your body may break down muscle. You’ll need to eat a good balance of vitamins, minerals, fats, carbohydrates, and protein.  

Learn more about healthy eating for active teens!


Feeling thirsty is not the first sign that your body needs water. In fact, once you are thirsty, your body has already lost fluids that you need. If you become dehydrated, this means that you have lost more fluids than you have taken in. Signs of dehydration are:

  • A dry or sticky mouth
  • Not being able to pass urine (pee) a lot
  • Urine that looks dark
  • Not being able to make tears
  • Low blood pressure
  • Rapid heart rate
  • Feeling irritable
  • Being disoriented
  • Feeling dizzy or weak
  • Having a headache

If you are dehydrated, you need to replace fluids right away. Water is the best choice to prevent dehydration. If you feel faint and/or dizzy every time you stand up (even after a couple of hours), and if you have very little urine output, you should tell an adult and visit the doctor.


Content last reviewed October 09, 2009
Page last updated October 31, 2013