If there is one “holy grail” secret to keeping your body healthy, it’s drinking plenty of water. The U.S. Geological Survey notes that water makes up as much as 60 percent of our bodies, and it’s responsible for everything from flushing out body waste to regulating body temperature.
“Our bodies are very dependent upon water, as all cells, body compartments, and bodily fluids (for example blood) within the human body contain water to some degree,” explains Albert Do, MD, MPH, a gastroenterologist and the clinical director of the fatty liver program at Yale Medicine in New Haven, Connecticut. He adds that our kidneys are good at managing the amount of water within our bodies; they make more urine in states of excess water intake, and they reduce urine production during periods of reduced water intake. But the body is more sensitive to states of water deprivation, and is generally not able to survive more than a week without water.
In addition to keeping you alive by helping your bodily systems function (which is obviously the biggest perk of staying hydrated!), water can also help you achieve a healthy weight. But it’s not as simple as water in, weight off. Here’s what you need to know about how water may help with weight loss or maintenance.
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What Does Science Say About Hydration and Weight Loss?
There is some scientific evidence supporting water as a tool for weight loss via a number of mechanisms. Dr. Do emphasizes that it is “not clear” that drinking water directly leads to weight loss, saying the two may be indirectly related.
Cynthia Sass, MPH, RDN, a board-certified specialist in sports dietetics based in Los Angeles, points out that water is just one piece of the weight loss puzzle, and she doesn’t recommend counting on it as a sole weight loss solution. “However, water is needed for every process in the body — including healthy circulation, digestion, and waste elimination — so drinking enough water benefits health in other ways,” she explains.
Water Consumption May Result in Less Food Consumption
One small study, published October 2018 in Clinical Nutrition Research, found that drinking water before meals helped naturally reduce calorie intake, which may in turn support healthy weight management. When subjects drank one and a quarter cups of water prior to a meal, they ate less compared with the groups who drank the same amount after a meal or drank nothing at all. This study involved only 15 participants, all of whom were between ages 20 and 30, so larger, more diverse studies are needed.
“In other words, drinking water before eating or with food may lead to reduction of food consumed and thus lead to weight loss,” Do explains. “Drinking water in the hour before eating a meal may allow time for hormonal signals of satiety to take effect and lead to less hunger at the time of eating.”
He also notes that increasing fiber intake before meals, or opting for multiple, smaller snacks throughout the day (rather than three larger meals) may have a similar effect.
Upping Water Intake May Help Speed Up Metabolism
A review of studies from June 2016, published in Frontiers in Nutrition, concluded that increasing water intake not only promoted weight loss via “decreased feeding,” but also helped speed metabolism by increased lipolysis (the breakdown of fats and other lipids by hydrolysis to release fatty acids).
“Research shows that water can help rev metabolism, and while the effect may be slight, it can snowball to create a greater impact over time,” adds Sass.
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How Much Water Should You Drink to Lose Weight?
Do says there is no specific amount of water that’s recommended for weight loss, because the relationship between the two hasn’t been scientifically proven. But “to maintain hydration balance,” he suggests following recommendations from the National Academies of Sciences, Engineering, and Medicine: 15.5 cups (3.7 liters or 124 ounces) for men and 11.5 cups (2.7 liters or 92 ounces) for women. This includes water and fluids from food, he says.
When Should You Drink Water to Lose Weight?
As for when you should drink water to maximize weight loss, prior to meals may help decrease your appetite and prevent overeating. And, because water can help with digestion, consider drinking some after a meal. In general, though, Sass recommends spreading your water intake throughout the day.
“Additionally, some drinks contain chemicals — such as caffeine — which stimulate urine production,” Do notes. In other words, they have an opposite, dehydrating effect. While you don’t need to switch to decaf for hydration purposes, he suggests trying to recognize when additional water intake should be considered — for example, in cases when you are exposed to hot weather or physical exertion — and make sure to rehydrate in response.
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How Can You Boost Your Water Intake?
As with other healthy lifestyle behaviors, incorporating water breaks into your daily routine can help you stick to the practice, suggests Do. “This could mean linking water intake to current habits (for example, drinking a cup of water after brushing teeth in the evening) or setting up reminders to do so.”
Another approach may be to add water-containing foods to your diet. The Mayo Clinic points out that many fruits and vegetables have a high water content, and highlights watermelon and spinach as two foods that are nearly 100 percent water.
Sass suggests keeping a water bottle with you, and setting reminders on your device to prompt yourself to drink. You can also enlist the help of a smart water bottle, like HidrateSpark, which calculates how much water you need to drink and keeps track of your consumption.
Finally, Sass suggests motivating yourself to drink water by infusing it with flavor. “If you’re not a fan of plain water, spruce it up with healthful add-ins, like lemon or lime, fresh mint, sliced cucumber, fresh ginger, or slightly mashed bits of seasonal fruit,” she suggests.
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What Is Water Weight (and How Can You Lose It)?
“Water weight is the fluid weight your body hangs onto,” explains Sass. And if you’ve ever started a diet and noticed the numbers on the scale dropping almost immediately, that’s likely due to the loss of water weight. Do adds that “body weight from water can vary from day to day and depends on one’s current hydration status, dietary habits besides water, geographic location including weather and altitude, and other factors.”
Water weight is often due to a higher than usual intake of sodium, because excess sodium triggers fluid retention, Sass continues. “Water weight can also be retained due to hormonal shifts,” she adds. If the water weight is due to excess sodium, ironically, “the best way to lose it is to drink more water, and up your intake of potassium, which triggers the release of excess sodium and fluid,” she explains. Potassium-rich foods include potatoes and sweet potatoes, bananas, avocados, and leafy greens like spinach, per the Cleveland Clinic.
From a health perspective, water weight is not harmful — in fact, it’s natural for the body to hold some water weight. Rather, weight from fatty tissue (also known adipose tissue or fat mass) is of concern for health. “Total body weight is a substitute measure for fat mass weight as the latter is difficult to directly measure,” he continues. “Fat mass quantity directly causes metabolic health issues such as elevated cholesterol, insulin resistance and diabetes, cardiovascular and fatty liver diseases.”
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Can Other Dietary Sources of Water Help You Lose Weight?
Water-rich foods — which include watermelon, strawberries, cantaloupe, peaches, oranges, cucumber, and even yogurt and cottage cheese — can provide about 20 percent of your total fluid intake, says Sass. Yet it can be hard to calculate water intake from food sources. “There is water in all foods [to various extents], so it can be difficult to measure exactly how much water one is drinking on a day-to-day basis,” Do says.
If you are trying to lose weight, you should also take into consideration the nutritional content of each food — including calories, carbs, and grams of protein — and how they will impact your overall diet.
Should You Try Water Fasting to Lose Weight?
Water fasting is a type of fasting that involves consuming only water. Sass doesn’t endorse the practice, “especially not on your own, without full medical supervision.” (There are certain circumstances in which your physician might recommend temporarily fasting prior to a medical procedure, like a colonoscopy, or for blood tests.)
Keep in mind that temporary weight loss may result from most liquid-based fasts and cleanses, including water fasting. But there is little to no scientific evidence of long-term weight loss on this type of eating plan. And, while temporary weight loss may be the only potential “pro” to doing a water fast, the “con” list is very long. Among the potential health consequences? Kidney damage, nutritional deficiencies, fainting, brain fog, fatigue, and, in women, hormone level alterations, Do says.
A Final Word About Hydration and Your Weight
Water is a crucial component to our overall health — after all, we literally need it to survive. But while drinking water can help you achieve your weight loss goals indirectly by reducing your caloric intake or speeding up metabolism, you can’t simply drink your way to a lower number on the scale.