To summarize the effect of drinking additional water on energy expenditure and diet outcomes.
Drinking sufficient water daily is very important for overall general health, but research has only shown modest benefits of drinking additional water for the purposes of weight control. Overweight and obese individuals on a low-calorie diet may see some increased benefit, but the effect size is unclear and more research is needed. However, given that there are very few drawbacks, additional water intake can be considered an additional tool for individuals struggling with weight loss or maintenance.
Two studies by Boschmann(2003; 2007) provided early evidence that drinking water alone could account for an increase in resting energy expenditure, and this has been referred to as the thermogenic effect of water. In the first of these studies, Boschmann found that drinking a half-liter of water in the absence of food increased the metabolic rate of participants by up to 30% for approximately an hour after drinking (with peak increase after 30-40 minutes). The researchers hypothesized that increased sympathetic activation after drinking was the mechanism that most likely explained the differences in energy expenditure.
Boschmann et. al followed up 4 years later with a randomized, controlled trial seeking to replicate these effects and found that 500ml of water increased energy expenditure by 24% for approximately an hour after drinking. These large effect sizes are striking because they suggest that the simple act of drinking an additional few liters of water per day could lead to significant weight loss over even the medium-term. Dubnov-Raz and colleagues replicated this effect in 2011 in a study with children, with one important difference being that these researchers used cold water (Dubnov-Raz, 2011).
Unfortunately, follow up research since these studies has found a significantly smaller thermogenic effect. They also discovered that the temperature of the water ingested may account for a significant portion of the variation in increased energy expenditure. In 2006, Brown et al. found that drinking cold water resulted in an increased energy expenditure of approximately 4.5% over an hour. Kocelak(2012) also used cold water and found an increase in energy expenditure between 12 and 20% after drinking cold water depending on the weight of the individual. The researchers concluded that the increase in energy expenditure was mostly related to heating the cold water to body temperature.
Charriere (2015) found that drinking distilled water led to an increase in energy expenditure of only 3%. Using distilled water is an interesting change in methodology, and it is possible that the water composition (distilled vs. tap, for instance) is a relevant factor in determining water's thermogenic effect. Girona (2014) found an increase of 2.3% (for room temperature water) to 2.9% (for cold water). Drinking body-temperature water (37C) did not result in a significant increase in resting energy expenditure.
In summary, most studies in the last decade have provided evidence for a real but relatively small increase in resting energy expenditure over baseline that is more pronounced as the temperature of the ingested water decreases.
Several systematic reviews have been published on this topic in the last 15 years, so we will take a brief look at two of them.
I generally found Muckelbauer(2013) to be the most helpful high-level summary of the issue. One of the main takeaways from this paper is the emphasis that the quality of the studies done on this topic has been poor in general. One reason is that there is a lack of controlled, randomized trials to effectively study this issue, and so it is difficult to properly establish causal links. Another issue brought up by the researchers is that there is a significant potential for bias since many of the studies providing some evidence for weight change with increased water consumption were at least partially funded by the water industry.
Another issue touched on is the fact that many of the studies on this topic focus on the replacement of high calorie beverages with water, and in my opinion those studies are not telling us anything very interesting. If you consume less calories each day as a result of drinking less soda, juice, and other calorie beverages, it is not a surprise that replacing these with water is associated with weight loss. Overall, the researchers found that the effects of drinking additional water on total energy expenditure were quite modest.
The mechanisms for the observed effects were hypothesized to be mainly explained by the hunger-suppressing effects of drinking water before meals resulting in less overall calories consumed over the course of the proceeding meal. Thermogenic effects of water are only briefly discussed, but the researchers suggest that this effect is likely only minor based on recent research.
Stookey(2016) provides a similar story. The overall effects of drinking additional water appear to be modest, but this paper focuses more heavily on individual differences and identifying which groups of people may benefit more significantly from increased water consumption with respect to weight change and fat oxidation. Unsurprisingly, the replacement of calorie beverages with water tends to provide the biggest effect size for overall energy expenditure, and we are already discussed why this is not particularly surprising or interesting.
However, the researchers identified a particular group of people who may especially benefit from increased water intake – overweight or obese individuals on a hypocaloric or low glycemic diet. This category likely covers the majority of people looking to lose weight, so it is particularly relevant to us. It is not yet clear from the research why overweight or obese individuals on a low calorie diet may see this increased benefit.
According to the paper, these conditions “would be hypothesized to accelerate weight loss by increasing energy expenditure and/or fat oxidation by reducing osmotic stress on cells, improving insulin resistance, reducing gluconeogenesis and/or improving postprandial glucose clearance”. A complete review of these possible mechanisms is beyond the scope of this article, but future research exploring these mechanisms in the context of water intake and weight loss in randomized, controlled trials would be interesting.
I was not able to find a reliable, trustworthy, and comprehensive source of information about this topic available online. Most of the available information topping search results on this topic is listed on unreliable sites without adequate references. Other articles have some reliable data but focus too narrowly on a single study or come to broad conclusions without proper support.
This article is an attempt to look at the available research, provide a decent summary on the topic, and provide a useful list of references for those seeking more information on the topic.
Boschmann, M., Steiniger, J., Hille, U., Tank, J., Adams, F., Sharma, A. M., … Jordan, J. (2003). Water-Induced Thermogenesis. The Journal of Clinical Endocrinology & Metabolism, 88(12), 6015-6019. doi:10.1210/jc.2003-030780
Boschmann, M., Steiniger, J., Franke, G., Birkenfeld, A. L., Luft, F. C., & Jordan, J. (2007). Water Drinking Induces Thermogenesis through Osmosensitive Mechanisms. The Journal of Clinical Endocrinology & Metabolism, 92(8), 3334-3337. doi:10.1210/jc.2006-1438
Brown, C. M., Dulloo, A. G., & Montani, J. (2006). Water-Induced Thermogenesis Reconsidered: The Effects of Osmolality and Water Temperature on Energy Expenditure after Drinking. The Journal of Clinical Endocrinology & Metabolism, 91(9), 3598-3602. doi:10.1210/jc.2006-0407
Charriere, N., Miles-Chan, J. L., Montani, J., & Dulloo, A. G. (2015). Water-induced thermogenesis and fat oxidation: A reassessment. Nutrition & Diabetes, 5(12). doi:10.1038/nutd.2015.41
Cruz, A. J., Bracamontes-Castelo, G., & Bacardi-Gascon, M. (2019). Effect of water consumption on weight loss: A systematic review. Nutricion Hospitalaria. doi:10.20960/nh.02746
Daniels, M. C., & Popkin, B. M. (2010). Impact of water intake on energy intake and weight status: A systematic review. Nutrition Reviews, 68(9), 505-521. doi:10.1111/j.1753-4887.2010.00311.x
Dennis, E. A., Dengo, A. L., Comber, D. L., Flack, K. D., Savla, J., Davy, K. P., & Davy, B. M. (2009). Water Consumption Increases Weight Loss During a Hypocaloric Diet Intervention in Middle-aged and Older Adults. Obesity, 18(2), 300-307. doi:10.1038/oby.2009.235
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Dubnov-Raz, G., Constantini, N. W., Yariv, H., Nice, S., & Shapira, N. (2011). Influence of water drinking on resting energy expenditure in overweight children. International Journal of Obesity, 35(10), 1295-1300. doi:10.1038/ijo.2011.130
Girona, M., Grasser, E. K., Dulloo, A. G., & Montani, J. P. (2014). Cardiovascular and metabolic responses to tap water ingestion in young humans: Does the water temperature matter? Acta Physiologica, 211(2), 358-370. doi:10.1111/apha.12290
Grading quality of evidence and strength of recommendations. (2004). BMJ, 328(7454), 1490. doi:10.1136/bmj.328.7454.1490
Institute of Medicine (2005). Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate. doi:10.17226/10925
Kocelak, P., Zak-Golab, A., Rzemieniuk, A., Smetek, J., Sordyl, R., Tyrka, A., … Olszanecka-Glinianowicz, M. (2012). The influence of oral water load on energy expenditure and sympatho-vagal balance in obese and normal weight women. Archives of Medical Science, 6, 1003-1008. doi:10.5114/aoms.2012.32406
Muckelbauer, R., Sarganas, G., Gruneis, A., & Muller-Nordhorn, J. (2013). Association between water consumption and body weight outcomes: A systematic review. The American Journal of Clinical Nutrition, 98(2), 282-299. doi:10.3945/ajcn.112.055061
Pan, A., Malik, V. S., Hao, T., Willett, W. C., Mozaffarian, D., & Hu, F. B. (2013). Changes in water and beverage intake and long-term weight changes: Results from three prospective cohort studies. International Journal of Obesity, 37(10), 1378-1385. doi:10.1038/ijo.2012.225
Parretti, H. M., Aveyard, P., Blannin, A., Clifford, S. J., Coleman, S. J., Roalfe, A., & Daley, A. J. (2015). Efficacy of water preloading before main meals as a strategy for weight loss in primary care patients with obesity: RCT. Obesity, 23(9), 1785-1791. doi:10.1002/oby.21167
Rolling Revision of the WHO Guidelines for Drinking-Water Quality. (2004, August). Retrieved from https://www.who.int/water_sanitation_health/dwq/nuthardness.pdf
Stookey, J. (2016). Negative, Null and Beneficial Effects of Drinking Water on Energy Intake, Energy Expenditure, Fat Oxidation and Weight Change in Randomized Trials: A Qualitative Review. Nutrients, 8(1), 19. doi:10.3390/nu8010019
Stookey, J. D., Constant, F., Popkin, B. M., & Gardner, C. D. (2008). Drinking Water Is Associated With Weight Loss in Overweight Dieting Women Independent of Diet and Activity. Obesity, 16(11), 2481-2488. doi:10.1038/oby.2008.409
Thornton, S. N. (2016). Increased Hydration Can Be Associated with Weight Loss. Frontiers in Nutrition, 3. doi:10.3389/fnut.2016.00018
Walleghen, E. L., Orr, J. S., Gentile, C. L., & Davy, B. M. (2007). Pre-meal Water Consumption Reduces Meal Energy Intake in Older but Not Younger Subjects. *Obesity, 15(1), 93-99. doi:10.1038/oby.2007.506