Soda and juices contain higher amounts of sugar than sport drinks and should be avoided during exercise. They can cause cramping, diarrhea, and nausea. Beverages that cause water loss from the body should be avoided as well. Examples of these include caffeinated tea and coffee. Thirst is a sign that dehydration has already occurred.
Clear urine is a sign of being well hydrated.
Therefore, a person weighing 120 pounds should eat about 300 grams per day. Carbohydrates are an important source of energy for the body. While fat stores would let them run for nearly 1000 miles, carbohydrate stores will limit the distance to about 15 miles. Since our bodies need carbohydrate in order to burn fat for energy, it is important that glycogen stores are well maintained. Therefore, individuals who exercise for prolonged periods of time, such as marathon runners, will require more carbohydrates.