Weight loss effects of water

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The apparent weight loss effects of water are still a subject for further research, but there is some evidence that suggests that drinking water can be associated with appetite reduction (for middle-aged and older people),[1] consuming fewer calories,[2] burning slightly more calories,[3] and eating more fruits and vegetables[fn 1]. Increased water consumption, or replacement of energy-containing beverages with energy-free beverages,[4] or consumption of water-rich foods such as fruits and vegetables with a lower energy density,[5] may help in weight management. Popular advice to children regarding water consumption is often inaccurate.[6]

This evidence has been used by some of the scientists who worked on this research, and by others, to bolster suggestions that people who are trying to lose weight can benefit from augmenting – but not replacing – their dietary programs by drinking water, either before meals or at any time. Such advice had previously been given by dieticians even before the most recent research was published.

In the case of appetite reduction, the apparent effect has been reproduced in a published study[1] in adults aged 55–75, half of whom were instructed to drink 500ml of water before every meal, while following a low-calorie diet. This behaviour led to the water-drinking cohort losing weight faster over a 12 week period. On average, the water-drinking cohort also continued to lose weight - although at a slower rate - over the following 12 month period, even though they had ceased their low-calorie diets. The study authors attribute this to the fact that those participants continued to drink water before meals.

Possible appetite reduction effect[edit]

Drinking water prior to each meal may help in appetite suppression. A promising[2] approach to reducing appetite which does not involve taking any drugs, and is very safe, is to drink a moderate amount of water before a meal.[2] Though this had been a folk remedy for overeating for many years, and is recommended by some dieticians[7] and stipulated in some scientific studies, it was only recently that the approach was subjected to a scientific randomised controlled trial to see how much effect it had.[8][9]

In a prior study[citation needed], researchers had found that water drinkers ate 75 to 90 fewer calories per meal.[7][9] However, they wanted to know whether this effect made a difference to weight loss, or whether it was cancelled out by subjects eating more through the day, and so they did a randomised controlled trial to find this out.[1][2]

Davy et al. randomised controlled trial[edit]

Davy et al.[1] took a group of 48 overweight and obese[1][2] Americans aged 55 to 75 who were considered inactive, and divided them randomly into two equal-sized[10] groups. The control group simply followed a calorie-controlled diet equating to approximately 1500 calories per day for the men and 1200 calories per day for the women. The second group followed exactly the same diet, but drank 500 millilitres of water before each meal.[8] Both groups kept up the diet for 12 weeks. Although both groups lost weight on average – as scientists would expect to happen, because such calorie-controlled diets are known to be effective – the water-drinking group lost about 5 pounds more on average, which made the diet 30% more effective.[2] Because the water-drinking group reported feeling both more full and less hungry, the researchers believe that the water acts to suppress appetite.[3][11] The researchers also recommended that people wishing to lose weight should replace sweetened calorie-containing drinks with water.[7][9][12]

Subjective effects also reported by the water-drinking group were a clearer mind and a better ability to think. There were no negative effects reported.[13]


A 12-month-long followup to this study was presented to a meeting of the American Chemical Society in August 2010. However, since this follow-up study has only been reported at a conference, and not yet published in a peer-reviewed publication, it must be treated as provisional. The followup found that while the control group had, on average, gained some weight after discontinuing the diet, the water-drinking group weighed, on average, slightly less than they did after discontinuing the diet.[2] The water-drinking group had voluntarily chosen to continue drinking water before meals, even though they were not following the strict diet any longer. This suggests that drinking water before meals is also effective in preventing weight loss rebound, if continued after the end of a diet.[8] Since many people experience great difficulty keeping weight off permanently after dieting, this could make the water technique more attractive.

Provisos and criticisms[edit]

Drinking more water is a pretty simple strategy that may be helpful to people trying to lose weight. We're not saying, "Drink more water and the body fat will melt away". But for people who are trying to lose weight and trying to follow a low-cal diet, it's something they can do as part of that.

—Senior study author Brenda Davy[2]

There has been relatively little research carried out on this topic.[3] However, this study is "promising", according to Barry Popkin, director of the University of North Carolina Nutrition Obesity Research Center (who has himself carried out empirical research on water and weight loss[2]).

The researchers caution that while drinking moderate amounts of water (as the subjects did in this study) is safe, drinking extremely large amounts of water over a short period of time can lead to serious health problems,[9] a very rare[13] phenomenon known as water intoxication.[11] It can cause low sodium levels,[13] seizures, swelling of the brain and even death.[7]

The study only looked at people aged between 55 and 75. The effect is not known to work in younger people: previous research[citation needed] has shown that in those aged 18–35, drinking more water at the meal did not cause them to eat fewer calories at the meal.[2] This is believed to be because water travels out of the stomach almost immediately in younger people.[2][14]

In the past, some believed that drinking at the same time as eating was unhealthy because it dilutes the stomach acid. In fact, studies[citation needed] have repeatedly shown that the acidity level of the stomach does not change very much when a person does this, and therefore it is not seen as a cause for concern.

Carla Wolper, an assistant professor in the Eating Disorders Center at Columbia University, cautioned that it can be more difficult to get people to follow dietary advice outside of a scientific study – so even if it works, people might not have the discipline to follow it. She noted that other simple things that people can do to lose more weight, such as cutting portion sizes and writing down what they eat, do work if followed, but it is very difficult to get people to carry out these simple actions.[2]

How it might work[edit]

As stated above, a hypothesis of Davy et al. (who conducted the original trial) is that the water reduces appetite. The water also displaced calorie-containing beverages in the diets of the water-drinking group in the trial.[3] However, Davy does not believe that this explains away the results of the trial, because both groups had to keep their calorie intake within predefined limits.[8]

Registered dietician Dawn Jackson Blatner, who was not involved in the study, says "Many of us confuse hunger and thirst signals so drinking water through the day and before meals makes sense to take the edge off thirst which leaves us with a more accurate feeling of true hunger."[3]

Concomitant dietary changes[edit]

Research by Barry Popkin et al. has shown that people who drink lots of water eat more vegetables and fruits,[15] drink fewer sugary beverages, and consume fewer total calories.[2][16] The reason for drinking less sugary beverages would likely be that the increased water substitutes for them in the diet, quenching the thirst so that the person does not feel as much need to drink sugary beverages.

Calorie burning[edit]

Some claim that drinking cold water aids in calorie burn as the body has to work to heat the cold water in the body and hence burning calories. This idea may be similar to the idea of eating Celery as a Negative calorie food. However the number of calories generated by drinking cold water may be minimal, since the body's response to cold conditions is to first reduce heat loss, not create new heat. It does this mainly by reducing blood flow to the skin, which reduces heat lost through the skin. If this isn't sufficient to maintain body temperature, new heat is created through shivering. A study[17] found that drinking that approximately 518 mL (18 ounces) of near-freezing water (3°C) only burned approximately 4 kcal, well below the theoretical energy cost of warming the water to body temperature.

A study in Germany[18] in 2003 reported that after drinking 17 ounces of water, the subjects' metabolic rates increased by 30%, starting at 10 minutes after water consumption, and peaking at 30 to 40 minutes. However, exercise physiologist Daniel Moser commented that the effect of this on weight loss would be "extremely modest", and said that more studies were needed to confirm the effect.[19]

A follow-up study[20] in 2007 by the same research center confirmed that drinking plain water does increase metabolism. Subjects burned approximately 23 kcal from drinking 500 mL of water.

However a study[17] by a different research center in 2006 failed to confirm that drinking water significantly increases metabolism. Drinking room temperature water had no effect on the metabolic rate, and drinking near-freezing water (3°C) raised metabolism by only 4.5%, much less than the 30% found by the other research center.


  1. ^ Eating more fruits and vegetables is often recommended by dieticians[citation needed] and governments[who?], both to aid weight loss[citation needed], and because of its other potential health benefits, such as a reduction in the risk of heart disease and type 2 diabetes[citation needed].

Further reading[edit]


  1. ^ a b c d e Elizabeth A. Dennis, Ana Laura Dengo, Dana L. Comber, Kyle D. Flack, Jyoti Savla, Kevin P. Davy and Brenda M. Davy (February 2010), "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, "Our objectives were to determine if premeal water consumption facilitates weight loss among overweight/obese middle-aged and older adults, and to determine if the ability of premeal water consumption to reduce meal EI is sustained after a 12-week period of increased water consumption." 
  2. ^ a b c d e f g h i j k l m Jenifer Goodwin (23 August 2010). "Could drinking water before meals help you lose weight?". BusinessWeek. Retrieved 27 August 2010. 
  3. ^ a b c d e Julie Deardorff (24 August 2010). "Health claim: Drinking water aids weight loss". Chicago Tribune. Retrieved 25 August 2010. 
  4. ^ "Beverage consumption and adult weight management: A review". Eat Behav 10 (4): 237–46. December 2009. doi:10.1016/j.eatbeh.2009.07.006. PMC 2864136. PMID 19778754. 
  5. ^ "The relationship between dietary energy density and energy intake". Physiol. Behav. 97 (5): 609–15. July 2009. doi:10.1016/j.physbeh.2009.03.011. PMID 19303887. 
  6. ^ Friedrich Manz, MD (2007). "Hydration in Children". Journal of the American College of Nutrition 26 (90005): 562S–569S. 
  7. ^ a b c d Fiona Macrae (24 August 2010). "A cheap weight-loss tip that really does hold water: Drink two glasses before every meal". Daily Mail. Retrieved 26 August 2010. 
  8. ^ a b c d "Obesity: Drink till you drop". The Economist. 24 August 2010. Retrieved 25 August 2010. 
  9. ^ a b c d "Drinking water before meals helps dieting, says study". BBC News. 24 August 2010. Retrieved 25 August 2010. 
  10. ^ Shari Roan (23 August 2010). "If all else fails, dieters, drink water". Los Angeles Times. Retrieved 27 August 2010. 
  11. ^ a b "Clinical trial confirms effectiveness of simple weight control method". Physorg. 23 August 2010. Retrieved 25 August 2010. 
  12. ^ "Drink two glasses of water before meal ‘to shed flab’". The Hindu. 24 August 2010. Retrieved 25 August 2010. 
  13. ^ a b c Anne-Marie Tobin (23 August 2010). "Tap on, weight off? Drinking water before meals aids in losing pounds: study". The Canadian Press, Online Edition. Retrieved 27 August 2010. [dead link]
  14. ^ Dr Jennifer Ashton, Harry Smith. Drink Water, Lose Weight. CBS. Retrieved 25 August 2010. 
  15. ^ Barry M. Popkin, Denis V. Barclay and Samara J. Nielsen, "Water and Food Consumption Patterns of U.S. Adults from 1999 to 2001", Obesity 13 (12): 2146–2152, doi:10.1038/oby.2005.266 
  16. ^ Jodi D. Stookey, Florence Constant, Christopher D. Gardner and Barry M. Popkin (December 2007), "Replacing Sweetened Caloric Beverages with Drinking Water Is Associated with Lower Energy Intake", Obesity 15 (12): 3013–3022, doi:10.1038/oby.2007.359 
  17. ^ a b "Water-induced thermogenesis reconsidered". 
  18. ^ Michael Boschmann, Jochen Steiniger, Uta Hille, Jens Tank, Frauke Adams, Arya M. Sharma, Susanne Klaus, Friedrich C. Luft and Jens Jordan (December 2003), "Water-Induced Thermogenesis", J. Clinical Endocrinology and Metabolism 88 (12), ISSN 0021-972X, PMID 14671205 
  19. ^ Salynn Boyles (4 January 2004). "Drinking water may speed weight loss". WebMD. Retrieved 25 August 2010. 
  20. ^ "Water Drinking Induces Thermogenesis".