Almost all sources will advise you to make sure that you drink enough water when trying to lose weight. Replacing plain water with sugar-containing drinks is one way to cut calories, and some studies indicate that it has additional effects on weight loss by reducing the calories you eat and helping you burn fat.
Cold water and burning calories
One theory is that your body has to burn calories to bring cold water to body temperature. A small 2003 study indicates that drinking more cold water can help you burn a few extra calories each day. They found an effect of burning an additional 50 calories per liter of cold water, which would be about 25 calories in a typical water bottle filled with cold water. The main effect comes from the fact that the body needs to warm the water in your digestive tract. It’s a minimal effect, roughly the equivalent of five regular M&M candies.
A follow-up study challenged the difference in calories between cold water and room temperature water. She found a weaker effect, about 5 calories per bottle of cold water, or just one plain M&M candy.
All other things being equal, if you prefer cold water, go ahead and chill it. Few people find room temperature water as pleasant, and you can drink less. The American College of Sports Medicine recommends that athletes and people who exercise exercise drink cold water because they will want to drink more.
How much water do you need each day?
The amount of water you need to drink each day, regardless of your diet, is a common question. In addition to the water in food, medical references indicate that women should drink approximately nine cups of drink per day (73 ounces) and men 12.5 cups (100 ounces). With exercise, you should replenish the water you lose through sweating.
Why should you drink more water when dieting?
Many diets advise you to drink more water when you want to lose weight. Drinking more water doesn’t just “flush out the fat” as it is sometimes claimed, but there are reasons to do so.
Drinking a full glass of water each time you are hungry and before a meal or snack briefly fills your stomach and makes you feel full and may allow you to stop eating earlier. Studies have sometimes shown that drinking water can reduce the number of calories you eat during a meal, but it’s not universal.
The breakdown of body fat and muscles during weight loss produces waste products which must be eliminated by the kidneys. It is important to drink enough water to keep the kidneys working and to clear up this waste.
Popular high protein diets produce more waste from digestion, and even less from the breakdown of stored fat. Kidney function is even more important with a high protein diet.
If you drink plain water, you’re less likely to drink something that has calories. What you drink is often a major source of unwanted calories. The key is to replace those unwanted calories with nutrient-dense foods.
The dangers of drinking too much water
Don’t start drinking an extra gallon of water a day. It can kill you, especially if you fast or eat very little. The absorbed water must be in balance with the body’s saline electrolytes. The body must maintain a balanced salt or it will lead to hyponatremia, which can lead to a heart attack and even death.
Drinking too much water has resulted in the death of healthy athletes. Drinking sports drinks during an endurance exercise aims to replenish the salt lost in sweat. Dieters should not throw themselves into liters of water a day in the hopes of burning a few extra calories. Drink a few more glasses, yes. But one gallon is too much.
Drink and exercise
Exercise, like walking, leads to increased heart rate and respiratory rate and loss of body water due to increased breathing and sweating. Walkers should drink a full glass of water an hour before walking, then drink about a cup of water every kilometer. When you are finished walking, drink a glass of water. To prevent hyponatremia, the marathon and half marathon guidelines now say “drink when you’re thirsty” rather than pushing the water. Make sure you have enough water during exercise to be able to drink when you are thirsty.