The more you exercise, the more fluid you’ll need to keep your body hydrated.
An extra 1 or 2 cups of water should suffice for short bouts of exercise, but intense exercise lasting more than an hour (for example, running a marathon) requires additional fluid. How much additional fluid is needed depends on how much you sweat during the exercise, but 13 to26 ounces (or about 2 to 3 cups) an hour will generally be adequate, unless the weather is exceptionally warm.
Hot or humid weather can make you sweat and requires additional intake of fluid. Heated indoor air also can cause your skin to lose moisture during wintertime. Further, altitudes greater than 2,500 meters (8,200 feet) may trigger increased urination and more rapid breathing, which use up more of your fluid reserves.
3. Illnesses or health conditions.
Signs of illnesses, such as fever, vomiting and diarrhea, cause your body to lose additional fluids. In these cases you should drink more water and may even need oral rehydration solutions, such as Gatorade, Powerade or Ceralyte.
[Ed. Note: Gatorade tests as being very acidic. I bet the others do too! Test before you drink is a good motto to adopt!]
Certain conditions, including bladder infections or urinary tract stones, also require increased water intake. On the other hand, certain conditions such as heart failure and some types of kidney, liver and adrenal diseases may impair excretion of water and even require that you limit your fluid intake.
4. Pregnancy or breast-feeding.
Women who are expecting or breast-feeding need additional fluids to stay hydrated. Large amounts of fluid are lost especially when nursing. The Institute of Medicine recommends that pregnant women drink 2.4 liters (about 10 cups) of fluids daily and women who breast-feed consume 3.0 liters (about 12.5 cups) of fluids a day.
5. When Weight Loss Is Water Loss
You’ve probably heard someone say at some time that the first pounds lost when starting a diet are “mostly water weight.” This, in fact, is generally true. When initially cutting back on calories or increasing exercise, an individual typically begins to use his or her energy stores of glycogen (stored carbohydrates) first. Glycogen is stored in the muscle tissue along with more than twice its weight in water.
Therefore, as a person begins to use this glycogen, the stored water that goes along with it is released and excreted in the urine.
Additionally, when increasing exercise, increases in sweating may occur, resulting in water loss through the pores.
If the lost water is not replenished, then the outcome will be lost weight in the form of water. This, however, is not a healthy way to lose weight and does not result in fat loss.
Athletes, especially, are encouraged to replenish their fluids as soon as possible after exercise. The rule of thumb is to drink two cups of water for every pound lost in a short period of time (within a day).
Remember: Two cups of water weigh one pound. If you exercise and lose a pound in a single exercise session, this is water weight—drink up and re- hydrate yourself.