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Drinking water prior to meals enhances weight-loss, suggests new study

Monday, August 24, 2009 Posted by Peter Janiszewski, PhD

It has often been recommended in popular weight-loss programs that overweight and obese individuals hoping to shed unwanted pounds should drink more water.

As is often the case, the evidence base behind this recommendation was rather scant. Fortunately, a new study published online in the journal Obesity suggests the recommendation may be quite sound.

In the study, Dennis and colleagues randomized overweight/obese older men and women to either a hypocaloric diet alone or a hypocaloric diet plus increased water consumption for a duration of 12 weeks.

The hypocaloric diet consisted of 1200 calories for the women and 1500 calories for the men. Those in the diet + increased water group were required to consume 500 ml of water (2 cups) 30 minutes prior to each of the 3 large daily meals (breakfast, lunch, dinner).

And what did they find?

While participants in both groups lost a significant amount of weight (5-8kg) in response to the diet, those who also consumed more water before their meals lost an additional 2 kg in comparison to the diet only group.

The greater weight loss in the group consuming pre-meal water could be the result of smaller caloric intake during each meal (~40 calories less per meal), as shown during the baseline laboratory test meals comparing no-water to water meal conditions in all the subjects.

While this is the first randomized trial to investigate the effect of increased water consumption on weight loss, the findings are in agreement with prior epidemiological studies showing that caloric intake in water drinkers is on average 200 calories less than among non water drinkers.

This study provides compelling evidence to encourage all those attempting to lose weight to increase their daily intake of water to help in their efforts. Specifically, one should consume approximately 2 cups of water, about half an hour prior to most meals.

As Travis has previously described, drinking more water will also have the added bonus of forcing you to take bathroom breaks, thereby increasing your level of physical activity.


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Dennis, E., Dengo, A., Comber, D., Flack, K., Savla, J., Davy, K., & Davy, B. (2009). Water Consumption Increases Weight Loss During a Hypocaloric Diet Intervention in Middle-aged and Older Adults Obesity DOI: 10.1038/oby.2009.235

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7 Response to "Drinking water prior to meals enhances weight-loss, suggests new study"

  1. Todd I. Stark Said,

    Interesting. I think Barbara Rolls says in "Volumetrics" that the liquid may not help if it is taken separately, at least based on triggering satiety mehanisms. She might have been too conservative? It sounds like it still has at least some satiation effect.

    Posted on August 24, 2009 at 2:14 PM

  2. darya Said,

    Cool story. I definitely find that sometimes I think I'm hungry when I'm really just thirsty. Will share this with my readers :)

    Posted on August 24, 2009 at 5:51 PM

  3. Anonymous Said,

    Or you could try the physicist's diet.

    I discovered why fashionistas rave about drinking gallons of water a couple of years ago, when I had cystitis - once I got up to 3l/day I didn't want to eat at all. Not fun though.

    Posted on August 24, 2009 at 6:17 PM

  4. Peter Janiszewski, PhD (Cand.), MSc Said,

    @ Todd - Yes, I have heard that before as well - the notion that you should drink water along with your meal to help enhance fullness earlier in the meal. Apparently, this is not always the case. I am unsure if there has been any comparison of fullness with different timing of water intake in other studies.

    @ darya - I agree, and I often have the same experience. I also used to drink tons of juice when thirsty - of course never considering the liquid calories I was consuming when I was simply dehydrated, not necessarily hungry.

    Thanks for spreading the news:)

    @ Anonymous That is quite an interesting suggestion. This study didn't consider water temperature as a potential confounder, but it is rather intriguing to think cold water may be more effective. I do remember reading somwhere that you tend to drink less when the liquid is cold - sort of more thirst quenching when cold - this could actually mean that it would be more effective using room temp water as you could drink more and fill up.


    Posted on August 24, 2009 at 7:42 PM

  5. Jan Said,

    Drinking 500 ml water did have a significant reduction on energy intake pre-trial. After twelve weeks this effect was gone. The watergroup did loose more weight and more rapidly, so the conclusion is that it works for the first couple of kilo's.

    The other interesting fact is the age of the population. We're talking senior citizens. The watertrick does not seem to have an effect on younger people(Walleghen EL van 2007).

    The suggestion that temperature has een effect, might be true. But at least on calorie expenditure. If you have one liter of water in the fridge at 7 degrees celsius and you would drink it. The body will warm it up to core temperature (37 degrees). Since a calorie is the amount of energy necessary to heat 1 gram of water 1 degree Celsius, it will burn 30 calories in the process, which is nothing but a funny thought.

    In practical sense drinking water before a meal will help seniors loose weight more rapidly in the first couple of weeks. Putting the water in the fridge will add another 45 calories per day (three meals). Since senior citizens tend to drink less often (because they are less mobile), it is a good behaviour pattern to learn. Don't expect anything from younger people.

    Posted on August 31, 2009 at 7:00 AM

  6. Sigrid Said,

    Sorry for being late, just discovered your site.

    Just wondering: If they were on a fixed-calorie diet how could drinking water influence their intake? 1200 calories is 1200 calories. If drinking water before every meal led to decreased food consumption this would mean they ate less than their 1200 calories, wouldn't it?

    And do you have other sources for drinking water as a fat-loss-aid? There was this meta-study by Heinz Valtin ( ) who couldn't find any reliable studies backing up this theory.

    Posted on December 1, 2009 at 7:42 AM

  7. Travis Saunders Said,

    @ Sigrid,

    In response to your first question, that is exactly right - drinking water helped people consume less calories. Although both groups were aiming at 1,500 calories for men, they were still free-living, so there was naturally some variability in the amount of calories that people consumed (according to diet records the water group averaged 1,454 kcal/day, while the non-water group averaged 1,511). In other words, if you want to go on a reduced calorie diet, consuming more water seems to help.

    As for the meta-analysis you describe, it actually wasn't looking at water as a weight loss aid. It was examining whether there was a scientific rationale behind the "8 glasses of water per day" message, which has never been targeted at weight loss. So while 8 glasses of water per day may not have much science behind it, drinking a glass or two of water before a meal does.

    Posted on December 1, 2009 at 9:29 AM


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We are PhD students in the School of Kinesiology and Health Studies at Queen's University in Kingston, Ontario. Our research focuses on the relationships between obesity, physical activity, and health risk. This blog is our attempt to consider the many "cures" for obesity that we read about on a daily basis. Enjoy.


The opinions expressed here belong only to Peter and Travis and do not reflect the views of any organization. Any medical discussion on this page is intended to be of a general nature only. This page is not designed to give specific medical advice. If you have a medical problem you should consult your own physician for advice specific to your own situation.

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