Base your diet on a variety of factors including your age, size and physical condition; and the type of exercise you are doing.

Hydration

Water is the most important factor in sports nutrition. It makes up about 60 percent of body weight and is involved in almost every bodily process. Your body cannot make or store water, so you must replace what you eliminate (i.e., urine, sweat). Everyone should drink at least two quarts (eight cups) of water each day, and athletes need more. Drink plenty of fluids before, during and after sports events to stay hydrated and avoid overheating. When you workout or compete, especially in hot weather, try to closely match the amount of fluid you drink with the amount you lose to sweat.

Some tips for staying hydrated:

• Drink small amounts of water frequently, rather than large amounts less often.
• Drink cold beverages to cool your core body temperature and reduce sweating.
• Weigh yourself after working out and drink 2-3 cups of water for every pound lost. Your body weight should be back to normal before the next workout.
• Pay attention to the amount and color of your urine. You should excrete a large volume that is nearly colorless. Small amounts or dark colored urine can indicate dehydration.

Eating a balanced diet is another key to sports nutrition. The right combination of fuel (calories) from carbohydrates, proteins and fats gives you energy for top performance.

• Eat carbohydrates for at least several days before exercise/competition, so you start with glycogen-loaded muscles.
• Eat more carbohydrates during exercise/competition lasting more than an hour to replenish energy and delay fatigue.

• Level of fitness: Physically active people need more protein compared with those who don't exercise. You also need more when you start an exercise program.
• Exercise type, intensity and duration: Endurance athletes often burn protein for fuel, as do body builders and others doing intense, strength-building activities.
• Total calories: Your body burns more protein if you don't consume enough calories to maintain body weight. This can happen if you eat too little or exercise too much.
• Carbohydrate intake: Your body may use protein for energy if you exercise with low levels of muscle glycogen or if you do repeated training sessions without eating more carbohydrates. When you start with enough muscle glycogen, protein supplies about 5 percent of energy. Otherwise it may supply up to 10 percent.

What you eat several days before endurance activities affects performance. Your food the morning of a sports competition can ward off hunger, keep blood sugar levels adequate and aid hydration. Avoid high protein or high fat foods on the day of an event, as these can stress the kidneys and take a long time to digest. Empty your upper bowel by competition time. General guidelines:

• Eat a meal high in carbohydrates.
• Take solid foods 3-4 hours before events, and liquids 2-3 hours before.
• Choose easily digestible foods (i.e., not fried).
• Avoid sugary foods/drinks within one hour of event.
• Drink enough fluids to ensure hydration (i.e., 20 ounces of water 1-2 hours before exercise, and an additional 10-15 ounces within 15-30 minutes of event.)

To avoid running out of carbohydrates for energy, some endurance athletes like long-distance runners, swimmers and bicyclists load their muscles with glycogen by eating extra carbohydrates in combination with doing depletion exercises several days before an event:

• First exercise to exhaustion. Your workout must be identical to the upcoming event to deplete the right muscles.
• Then eat a high-carbohydrate diet (70-80 percent carbs, 10-15 percent fat, 10-15 percent protein) and do little or no exercise starting three days before your event.
• Muscles loaded with unused glycogen will be available to work for longer periods of time during competition.