You must have noticed advice from almost every source that you should ensure you are Drinking enough water when trying to lose weight. Substituting plain water for sugar-containing beverages is one way to cut Calories, and some studies say it has additional weight loss effects in reducing the calories you eat and helping you burn fat.

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One theory is that your body must burn calories to bring cold water up to body temperature. A small study from 2003 says drinking more cold water may help you burn a few more calories each day. They found an effect of burning 50 more calories per quart (liter) of cold water, which would be about 25 calories in a typical water bottle full of cold water. The effect mostly comes from the body needing to heat up the water in your digestive tract. It’s a small effect, about the equivalent of five plain M&M candies.

A follow-up study disputed the difference in calories between cold water and room temperature water. It found a smaller effect, about 5 calories per water bottle full of cold water, or just one plain M&M.

With all things being equal, if you prefer cold water, go ahead and chill it. Few people find room temperature water as palatable, and you may drink less of it. The American College of Sports Medicine recommends that athletes and people engaged in exercise drink cooled water as they will want to drink more of it.

How much water you should drink each day regardless of dieting is a common question. Other than the water you get in food, medical references say women should drink about nine cups of beverages each day (73 ounces) and men should drink 12.5 cups (100 ounces) of beverages. With exercise, you should replenish the water you lose through sweat.

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Many diet plans advise you to more drink water when you want to lose weight. Drinking more water doesn’t simply “flush fat” as is sometimes claimed, but there are reasons to do so.

• Drinking a big glass of water whenever you feel hungry and before a meal or snack fills the stomach briefly and makes you feel fuller and perhaps stop eating sooner. Studies have sometimes found drinking water to reduce the calories you eat during a meal, but it is not universal.
• Breaking down body fat and muscle during weight loss produces wastes that must be eliminated through the kidneys. Drinking enough water is important to keep the kidneys functioning to remove these wastes.
• Popular high-protein diets produce more waste products from digestion, let alone from breaking down stored fat. Kidney function is even more important when on a high-protein diet.
• If you’re drinking plain water, you are less likely to be drinking something with calories in it. What you drink is often a big source of junk calories. The key is to replace those junk calories with food that is high in nutrition.

Don’t start drinking an extra gallon of water a day. That can kill you—especially if you are fasting or eating very little. Water taken in must be in balance with body salt—electrolytes. The body needs to maintain salt balance or risk hyponatremia, which can result in a heart attack and even death.

Drinking too much water has caused the deaths of healthy athletes. Drinking sports drinks during endurance exercise is meant to replenish salt lost in sweat. Dieters should not plunge into drinking gallons of water a day in hopes of burning a few more calories. Drink an extra few glasses, yes. But a gallon is too much.

Workout routine such as walking causes your heart rate and breathing rate to rise and you lose body water through increased respiration and sweat. People who walk should drink a large glass of water an hour prior to walking, then drink about a cup of water every mile. When you finish walking, drink another glass of water. To prevent hyponatremia, guidelines for the marathon and half-marathon now say to “drink when thirsty” rather than pushing water. Be sure to have access to enough water during exercise so you can drink when you feel thirst.