How can you lose weight by drinking more water?
We all have heard or read somewhere that drinking more water will enhance your weight loss.
In my previous post, How Many Ounces of Water Should I Drink Daily?, we see that for normal individuals under normal conditions, risk of dehydration is not relevant, and so consciously targeting any amount of water each day for this purpose is futile and redundant. As one should expect, we can trust our bodies to do the job of keeping us hydrated without specific intervention.
What about water for weight loss? Is there sufficient evidence to conclude that we could accelerate weight loss by drinking more water?
The answer is yes.
Does this mean that it is worth the effort to deliberately drink more water?
Research shows that water can accelerate weight loss on two fronts:
- Thermogenesis: water induces a calorie-burning metabolic response
- Calorie Control
Let's break it down...
One common argument in favor of increasing water intake to lose more weight: water-induced thermogenesis – does drinking water elicit a calorie-burning metabolic response?
Dr. Michael Boschmann and his team recruited 14 health subjects (7 male, and 7 female), to a study that investigated metabolic consequences to water consumption. Among various metrics being measured and analyzed, Boschmann was able to determine that drinking water at room temperature increased caloric expenditure by as much as 30% over a 90-minute period.Interestingly, fat metabolism doubled in men, but not in women – however the fat did not come from the subcutaneous abdominal region (stubborn fat). Finally, using a subgroup of 4 individuals Boschmann showed that ingestion of body-temperature water instead of room-temperature induced a ~40% less caloric expenditure . If we hold everything as perfect and true, based on the results, in day for every 500 ml bottle of water consumed in a day, one would burn an extra ~17 calories. Over a year that would translate to nearly 2 pounds of body-fat. This is 60 – 70% independent of water-temperature induced thermogenesis, but still implies that drinking colder-than room-temperature water should boost caloric expenditure even more so.
It should be made clear, however, that this is one of many studies on whether water elicits a thermogenic response... the data is quite conflicting and so it is possible that room temperature water is not very effective for burning extra calories .
How does water help reduce calorie intake?
What does water consumption have to do with calories? The two common arguments:
- You eat less when you drink water before or with a meal
- You drink less sugar-sweetened beverages when you drink more water
Let's dive further in now...
Does drinking water make you eat less food?
Plenty of controlled studies over the past 2+ decades show that fluid intake before or with a meal does not reduce food intake across multiple demographic types [3, 4, 5, 6]. Many of these trials were conducted by Dr. Barbara Rolls at Penn State University.
More recently, Rolls participated in a couple of studies that recruited participants and tested the impact of various beverages on food intake, once a week for 6 weeks. They had confirmed that it didn't matter whether the beverage was water, soda, diet soda, juice, or milk; participants still had consumed the same amount of food, when allowed to eat as much as they wanted. Even when the beverages were 18 fl oz instead of 12 fl oz, there was no impact to food satiety [7, 8].
Modern short-term studies tell us one thing...
The evidence is not so clear, however, because researchers from the Department of Human Nutrition, Foods, and Exercise, at Virginia Tech, pointed out that previous studies would typically compare various beverage-types as the preload, but had not clearly compared a water-preload to a no-water-preload on food intake.
One of their study’s, published in 2007 demonstrated that young adults will eat the same amount of food at a meal, independent of whether or not they have a water beverage 30-minutes before lunch. Strangely, in this particular trial, older men consumed about 100 calories less at lunch time with the water preload, but older women ate the same in both the preload and no-preload groups .The team ran another study with a similar design in older obese adults only. Consumption of 500 ml water 30-minutes before breakfast resulted in a 13% average decrease of caloric intake. This time the results were consistent among both genders .
Semi-Long-term studies tell a different story...
This data gave them cause to explore whether drinking water would decrease caloric intake at a meal soon after, consistently over a 12-week reduced-calorie diet, in overweight/obese adults. Subjects were divided into two groups:
- A group that was instructed to consume one 500 ml bottle of water (Aquafina was provided) prior to each meal 3 times per day.
- A group was received no such instructions but were still provided with water.
Participants in the water-preload group lost about 4.4 pounds more (~2% more weight lost, 1.3% being from fat). The interesting part is that water was the only difference between the groups over 12 weeks. They reduced calories from food and beverages similarly, independent of water intake. This would imply that increased water consumption has a causal relationship with greater weight loss .
These results are not surprising, however, since we already know that non-dieters would potentially be expected to burn an extra 5 -6 pounds worth of calories each year, from consuming 1.5 liters of water per day . Could it be that dieting combined with water intake somehow increases the energy expenditure associated with water metabolism?
This study also shows us that once someone is dieting, the amount of water being consumed does not affect how much food is going to be eaten, which they confirmed by running an 'ad libitum' test meal at the beginning and end of the 12 week period.
Longer-term studies give us better clarity...
The same team from VTech observed 173 premenopausal and overweight women for over a year while they were on various diets. They found consistent results that increased water intake led to significantly greater weight loss. Using various regression models, they were able to determine that the enhanced weight loss was partially due to a greater reduction in calorie-sweetened beverages; a finding not consistent with their previous research .
Large data pools can make it even better...
What we have at this point is a fair amount of complicated and conflicting information.
Fortunately Daniels and Popkin, from the Department of Nutrition at UNC, combined data from all studies that matched their inclusion criteria, and did a systemic review of the data. After determining average caloric intakes from all the literature, they published their findings in 2010 :
- Removing water from a meal does not alter how much food is consumed, except slightly in older people.
- Replacing water with sugar-sweetened beverages at a single meal, increased total calories consumed by an average of ~8%.
- An even larger increase –an average of 15% - in total caloric intake at a meal was observed when water was replaced with milk or juice, albeit from a smaller data pool.
We clearly see that the habit of replacing calorie-containing beverages with water promotes overall decrease in caloric intake, and thus greater weight loss, while having no impact on actual food intake.
The evidence is clear that an increase in (colder) water intake leads to greater weight loss, if all other variables are equal. Based on my own personal observations, however, this information will be misused and abused.
There is no "right way" to lose weight "faster." The obsession with finding quick-fixes, and/or an all-or-nothing approach, leads to many unfavorable consequences.
The first step is to establish a consistent eating lifestyle that works for you and promotes long-term success. Once that's in check you may then look for other ways to further optimize.
When all the data is weighed out, however, we see one point stand out more than others. Generally swapping out calorie-loaded beverages (i.e. juice, milk, sugar-sweetened, and even protein shakes/smoothies) for water will save many calories over time and promote weight loss.
But - what if you don't want to let go of your sweetened drinks? Can you switch to the diet version and still get the same results? We'll find out with my next post...
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2. Brown CM, Dulloo AG, Montani JP. Water-induced thermogenesis reconsidered: the effects of osmolality and water temperature on energy expenditure after drinking. J Clin Endocrinol Metab. 2006 Sep;91(9):3598-602. Epub 2006 Jul 5. PubMed PMID: 16822824.
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