It's no secret that we could all probably stand to drink more water. Before you roll your eyes and tell me that you know this already or that you don't know how much water you should actually be drinking, be advised that water is one of the easiest ways for you to feel better, look better. and smile more. All that work you do with diet and exercise...you can pretty much get the same results by drinking enough water! Ok...not quite, but diet and exercise is a whole lot easier when you are properly hydrated.
But how do you know if you should drink eight glasses of water a day? A gallon? More? Less? Here's some actual science and a method to figure out how much water you should be drinking.
Hydration and Athletic Performance
You've probably heard from your doctor/mom/science teacher that your body is made up of 60-75% water. Water is essential to many processes in our body like digesting food, transporting nutrients to our cells, regulating body temperature, keeping our joints healthy, keeping our skin looking young, and making sure that we have regular bowel movements.
When you start feeling thirsty, chances are that you are already dehydrated.
The "usual" guidelines given to coaches and fitness professionals is that a person should drink about two liters of water per day. The Institute of Medicine recommends that men should be consuming about 3.7 liters (125 ounces) of water each day and women should have 2.7 liters (91 ounces). This isn't too far off from the popular eight cups a day recommendation, except this one is actually backed up by evidence. They also say that about 80% of this comes from drinking and the other 20% generally comes from food. This recommendation does not account for people who are active or live in hot climates (they lose more water through sweat).
Exercise and heat increase demand for fluids. When the body works harder, heat is created, which needs to be lost. About 75% of the energy used in exercise produces heat and the remaining 25% goes toward useful work. Heat loss occurs when we perspire and when we exhale. Although it is common to think of dehydration in the context of heat and exercise, if the environment is dry, then significant fluid loss can also occur through the skin and exhaled breath.
A decrease in fluid of 2% can result in decreased athletic performance by as much as 10-20%. This is a significant amount especially when you consider the amount of effort you have to put into training to improve by just 5%. All of that work can be lost by simply from inadequate hydration.
Water also cools the body through perspiration. A lack of water reduces perspiration which leads to fatigue. As fluid intake is decreased, the body is less able to sweat and so internal temperature continues to rise. If this cycle is not corrected, overheating or hyperthermia can occur.
How Much to Drink
A general rule is to drink about 500ml of fluid per hour of vigorous exercise on top of the the two liters per day you should be drinking to maintain baseline fluid balance. In reality, this requirement varies from person to person. The best way to determine your need is to measure yourself. One liter of water weighs one kilogram. By measuring your weight both before and after training and correcting for any fluids taken in during exercise, you will get your individual rate of fluid lost for those conditions.
For example, a 70kg athlete who loses 200 grams during a one hour training session while drinking a 500ml drink will have a total loss of:
(Finish weight - start weight) - (weight of amount drink) or 69.8 - 70.0 - 0.5 = -0.7kg or -700g
This total loss is equivalent to 700mL of fluid per hour. This number can help you plan your fluid needs during training or a race. Further adjustment is needed if the conditions of the test training were to change.
Dealing with Dehydration
Hydration starts before a training session or race. In the morning, your body is most likely slightly dehydrated, so it is important to drink as soon as you get up. During long training sessions or races, it is best to sip water or sports drink frequently to keep pace with the rate of loss. Taking smaller drinks more frequently can also help prevent feeling full or bloated.
At the end of a race, your body may still be slightly dehydrated so it's important to drink afterwards to help replenish body fluids as well as help the body flush any accumulated metabolic waste products.
Here are some tips to help you get more water into your body ! Water is essential to almost every process in your body, so make sure you get enough!
- If you drink soda (which you shouldn't), make sure you have had at least 4 glasses of water before you allow yourself to drink a soda.
- Drink a glass of water at transitions during you day - when you get up, before you leave the house, when you get to work, before you eat lunch, when you get back from lunch, before you leave work, when you get home, and before you go to bed.
- Set a timer while you are exercising if you have a hard time remembering to drink while you are exercising.
- Make it easy by having a big water bottle near you throughout the day.
- Keep track. Make yourself a chart with boxes to fill in or check marks. There are even apps that will help you track your intake (I use the FitBit app).
- Freeze fruit to use as ice cubes. Frozen lemon, lime, or orange slices will not only keep your water cold but also give it a little flavor and some electrolytes.
- Make it a competition. Have a contest in your office to see who can meet their daily water intake goal. Have prizes or just allow the winner bragging rights. Make it last all week for a bigger challenge.
- Drink a glass of water before you have a snack. People often mistake thirst for hunger. If you are still hungry 15 minutes after drinking the glass of water, then have a snack.
- Have a cup of (decaf) tea to mix it up, especially in the winter when it's cold out. Caffeine is a mild diuretic so drinking caffeinated beverages is actually counterproductive to hydrating yourself.