Lose More Weight by Drinking More Water

Water Helps You Burn Fat and Drop Pounds

By Dan Gwartney, M.D.

It is incredibly simple to gain body fat. In fact, it is so basic that it commonly happens without intent; even worse, it happens when a person is trying to avoid fat gain. Surely, if a problem arises so naturally and simply, the solution must be equally simple and natural.

As has been demonstrated by the escalating obesity pandemic that threatens to overwhelm the Unites States health care system and has been exported to other Western cultures, preventing fat gain does not have a simple solution. In fact, it appears to be nearly unstoppable. Unfortunately, obesity also follows poverty, so it is no surprise that greater numbers may progress to overweight/obese status given the global pandemic and ongoing health, economic and financial crises that loom over the future of the Unites States.

Obesity is not inevitable, though; weight loss is possible, and it is even easier to maintain a healthy weight. Fitness-oriented individuals often have a more narrow focus, seeking fat loss rather than non-specific weight loss. The formula for fat loss and fat gain prevention is not a single variable equation. The obvious lifestyle foundations to fat loss are a hypocaloric diet (consuming fewer calories than your body burns throughout the day) and exercise. Two less obvious keystones that are nearly always overlooked are sleep and water intake. A previous article looked at the state-of-the-art understanding on the relationship between sleep and weight gain. [The CliffsNotes summary is if you sleep less than 6 hours, it promotes weight gain. It is best to get between 7½ to 8½ hours of sleep nightly.]

There was a time when water intake was often scoffed at by experts and pseudo-experts. That was before the bottled water era arrived, and the phenomenon swept across the nation, resulting in millions of gallons of triple-filtered, ozone-treated or reverse-osmosis purified water passing through the kidneys of the nation. At one point, the pendulum swing peaked with some people imbibing so much water that they managed to become water-toxic. The most well-known cases involved people coerced into drinking insane amounts of water during radio promotions or fraternity hazing; some died.1-3 In some circles, as waistlines grew bigger, the focus on water consumption has waned. However, is it right to allow water’s place to evaporate, especially in this culture of obesity?

Obviously not, since this post is dedicated to the role of water consumption in fat loss. Yet, people drink water every day, and still they gain weight. Society grew fatter even during the “thirsty years while carrying their bottled water during those arduous treks across office halls, and engaging in everyday activities. What evidence is there that water can accelerate fat loss? Exactly how potent is this proposed fat-loss effect of drinking water?

To be clear, drinking water is not to be portrayed as a fat-loss dynamo. As might be expected from everyday experience, drinking water holds the promise of offering mild support in fat loss. However, as fat gain is a gradual process for most that accumulates over years, ignoring the additional preventative support of water consumption is foolhardy. For those seeking to maximize fat loss, every little advantage counts toward ensuring success, so paying attention to water’s potential is practical.

A Flood of Research

A review of the medical literature shows a fair number of studies demonstrating water’s effect on fat-loss mechanisms in the body.4-7 Some of these are tangential, showing questionable associations between drinking water and fat loss. A correspondence between researchers was published in the International Journal of Obesity, in which one group raised the question as to whether weight loss seen with ACE inhibition (angiotensin-converting enzyme, a physiologic mechanism used to maintain blood pressure) in animal studies could have been due to increased water consumption.8 The correspondents to the question, Drs. Mathai and Weisinger, noted the observation present in other studies in addition to their own and addressed the issue from several points.9

ACE inhibition reduces the release of a posterior pituitary hormone called vasopressin; vasopressin constricts the blood vessels and reduces urine output when the blood pressure is low.10-12 Obviously, if one of the signals of low blood pressure (angiotensin II) is blocked, then the stimulus to release vasopressin would be reduced as well, allowing for greater urine output and stimulating the need for more water consumption. Indeed, the rats in the ACE-inhibition group drank twice as much water as control mice in Mathai and Weisinger’s study.4 Interestingly, ACE inhibition also appears to improve insulin sensitivity as well as promote fat metabolism in cells.8

Drs. Thornton, Even and van Dijk, the group who initially queried Mathai and Weisinger, pointed out the example of a genetic strain of rats (Brattleboro) that do not produce vasopressin.5,8 These rats consumed more than four times the amount of water the control mice did in Mathai and Weisinger’s study and are a leaner, slower-growing strain that has lower leptin concentration (a sign of fat stores).

Thornton, et. al, suggest that the association of increased water consumption and a protective effect against obesity be studied. They also noted that cellular dehydration inactivates mTOR signaling (a common pathway in many anabolic processes).8,13 This suggests that cellular hydration could protect against fat gain, improve insulin signaling and other metabolic functions.

Mathai and Weisinger responded by noting that increased water consumption could lead to calorie loss by increasing metabolic demand to warm the water from room temperature to body temperature (remember, a calorie is a unit of energy that represents the amount of energy it takes to raise one ml of water one degree Celsius); also the rats would be moving back and forth to the water bottle, increasing the amount of activity.9

Further, it was noted that like ACE inhibition, increased water drinking would inhibit vasopressin release. Vasopressin has been shown to reduce thermogenesis (heat production).8,14 In mice that are genetically engineered to be unable to respond to vasopressin, an increase in fat burning is also noted.9,15 However, Mathai and Weisinger noted that mice studies that chemically block angiotensin signaling and restrict water still show a weight-loss effect.9,16,17 This strongly suggests that ACE inhibition has several mechanisms affecting fat loss, in addition to stimulating greater water consumption. In fact, it is suggested that much of the fat-burning effect of ACE inhibition occurs in the liver, suggesting the liver plays a key role in the ACE inhibition, vasopressin, and water consumption associated with weight loss.

A set of studies performed by Dr. Michael Boschmann and his colleagues in Berlin demonstrated the true fat-loss potential of drinking water. The researchers showed that in normal-weight adults, drinking 500 ml of water (a little over 16 ounces) resulted in a 30 percent increase in metabolic rate for 60 minutes.18 Not only did the body have to increase its metabolism to warm the water up to body temperature (just like a water heater tank turning on after a bath to heat up the reservoir as it refills), but the change in osmolality (a measure of blood dilution) also increased the sympathetic tone. In other words, as the blood in the circulation was diluted by the large intake of water, adrenalin and norepinephrine were released to deal with the challenge. This adrenalin surge acted on the body like a mini-dose of ephedrine, increasing heat production by burning more calories. In men, the calories came from fat; in women, the increase in calorie burning consumed carbohydrates.18 This information holds a great deal of practical value for active individuals and weight trainers, as water consumption is healthy, extremely inexpensive and certainly effective based upon these results.

Water and Obesity

Boschmann’s group expanded the study in another paper that looked at obese and overweight individuals.19 Not only did he have the subjects consume 500 ml of water, he also looked at the same group consuming 50 ml of water, as well as 500 ml of saline. Saline is basically salt water; its purpose in the study was to see if the metabolic change was the result of a change in osmolality. Saline does not dilute the blood, so if the metabolic effect was due to a dilution, it would not be seen with saline. If it is a result of volume expansion (increasing the amount of fluid by 500 ml without changing the osmolality), then the metabolic effect would be seen in both groups. The 50 ml water challenge was to see if the body was sensitive to a very small change in osmolality and/or volume.

Based upon the discourse between Thornton et al. and Mathai et al., one would expect the metabolic increase to be seen in the water-drinking groups only, assuming overweight and obese people respond the same to the challenge as their normal-weight counterparts. In fact, that was what was observed. Drinking 500 ml of water caused the subjects to increase metabolism by 24 percent, nearly the same as the earlier study with normal-weight subjects; 500 ml of saline had no effect, nor did the 50 ml water challenge.19

Boschmann et al. concluded that the increase in energy expenditure (calorie burning) was a function of diluting the blood through water consumption, and not dependent upon volume or stretching the stomach.

What makes this an example of the wonder of the design of the human body is the simplicity and directness of the effect. Water is fairly rapidly absorbed. Imaging of the subjects showed that 75 percent of the water was absorbed in the first 40 minutes.19 Thus, in a short period, the stomach is expanded (causing a slight increase in thermogenesis via sympathetic stimulation – greater calorie burning), and the circulation carrying blood from the stomach and intestines to the liver is quickly diluted. This section of blood flow is a special “circuit” in the body. Called the portal circulation, veins from the lower portion of the stomach and the intestines drain into a large collector vein called the portal vein. The portal vein drains directly into the liver, rather than going back to the heart like the rest of the circulation. The liver (and intestines to some degree) is responsible for detoxifying the food, drugs and junk that get consumed in the modern diet.

Specific to this example, the portal circulation also signals the relative dilution or concentration of “stuff” in the portal blood. If the portal blood is very concentrated, it suggests to the body that food has been consumed and the body should prepare itself to store the incoming calories. If the blood is diluted, it suggests the “gut” is empty and that the body should switch over to using stored calories. One organ that is a central player in what energy source is used (stored versus incoming) is the liver. Being directly in line with the portal circulation, it is likely that the liver is strongly influenced (in the short term) by changes in portal blood dilution.

This dilution effect likely enters the peripheral circulation (blood flow to the body) and affects central circulation (blood flow of the brain) rapidly as well. If the osmosensors (the sensors that detect how diluted/concentrated the blood is) pick up on a sudden dilution, vasopressin is suppressed … and this is where we started.

Water and Fat Burning

How big a deal is drinking water for burning fat? For lean men, it may make a real difference; for lean women, it will burn extra calories; for the obese and overweight, it will increase the metabolism and support other weight-loss efforts. How hard is it to take advantage of, and is it something that can be done without a great deal of hassle? These subjects were measured in the morning; they had not eaten for approximately 13 hours and had not had anything to drink for 90 minutes – also, they avoided caffeine and nicotine for 48 hours.

Does this mean people have to avoid eating half the day or never have coffee again? Well, it would seem that one could use this dilution spike trick a couple of times a day. Perhaps waiting four hours after eating to allow the meal to pass well through the digestive tract, and avoiding drinking for 90-120 minutes to allow the portal circulation to reach a concentration baseline would prime the system. Interestingly, while 50 ml of water had no effect, 500 ml clearly did, raising energy expenditure by 30 percent in fit people. It would be interesting to see if there is a dose-response curve that would plot maximal, safe, effective. It is possible that consuming a full liter (1,000 ml) as opposed to 500 ml may offer a greater effect.

Most gym members have seen muscleheads walking around the gym carrying one-gallon jugs of distilled water, and taking big gulps during their workouts. While the intent there is usually sodium flushing to tighten skin, it is possible that there is also an unintended benefit of boosting metabolism by diluting the blood. As far as fat loss goes for the rest of us, keeping well hydrated will suppress your appetite, which is something that everyone who wants to lose fat or maintain a healthy weight should keep in mind. Often, the body is dehydrated and this is mistaken for hunger. Drink more water and you will eat less and stay leaner.

Even though the body is approximately two-thirds water and it is considered the safest thing to drink, it can harm if consumed in excess. As in all things, use common sense and avoid drinking in excess of one liter per hour as this approaches the functional limit of the kidneys. It is also important to get in plenty of electrolytes to compensate for the sodium, potassium, etc. that will be lost in the urine.

Remember to stay fully hydrated and consider a liter of water first thing in the morning to help kick-start your metabolism. A little caffeine could certainly aid in the fat-burning response if you can tolerate it. Stay safe, stay healthy and plenty of drink water. And remember that hydration is a key element to maintaining a healthy immune system, so besides helping you maintain a healthy weight, drinking water and staying fully hydrated will keep you healthier in the bigger picture.


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2. May M. Fraternity pledge died of water poisoning. San Francisco Chronicle 2005 February 4. http://www.sfgate.com/cgi-bin/article/article?f=/c/a/2005/02/04/HAZING.TMP

3. Nevius CW. A stupid radio stunt’s tragic finale. San Francisco Chronicle 2007 January 18. http://www.sfgate.com/cgi-bin/article/article?f=/c/a/2007/01/18/MNGMMNKOHS1.DTL

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