How does drinking water affect weight loss?

Our last blog about Downsize Me’s 7-day intensive water challenge showed some interesting motivators and perceived benefits of drinking more water.

Now, we want to talk about the two key ways that water affects weight loss.

Because, while nobody specifically mentioned weight loss as a motivator to drink water in our challenge, studies show that regular water drinking is actually a pretty important part of losing weight.

How does drinking water affect weight loss?

It’s hardly surprising that very few studies have been completed on the relationship between water drinking and body weight.

How Does Drinking Water Affect Weight Loss? | Downsize Me

Popkin et al (2010) says “there is extensive literature focusing on the effect of sweetened beverages on weight and obesity, diabetes and heart disease,” but no examination of the impact of water intake on health.

Probably, there’s not money in that kind of study. Do you think?

Nevertheless, the authors found a handful of studies show that when subjects replaced sugar-sweetened drinks, juice or milk with water, they lost weight due to a reduced energy (calorie) intake.

Is this significant?

Yes, absolutely, because in that study, they found that drinking water instead of calorie-containing drinks saved about 10 – 13% of total daily energy intake.

Which prompts me to ask:

What would happen to body weight if everyone consumed 10 – 13% fewer calories?

Are Diet Drinks an Acceptable Substitute For Water?

How Does Drinking Water Affect Weight Loss? | Downsize Me

I’ve just mentioned calories, so you might be thinking, “well then artificially-sweetened, zero-calorie drinks should be a great way to reduce calories, right?”.

Maybe not.

A 2015 study by Madjd et all studied a group of overweight and obese women who were asked to drink either plain water, or artificially-sweetened beverages, for the period of the study

The women who drank water reported greater (significant) changes in weight and fasting insulin compared to women drinking the artificially-sweetened beverages.

How Does Drinking Water Affect Hunger and Satiety?

Comprehensive data from a German school indicates that their intervention to increase water by 1.1 glasses/day, actually reduced the children’s risk of overweight by 31% (these were statistically significant results).

A 2105 Study by Parretti et al studied a group (84) of obese adults to work out whether they could curb appetite.

  • The test group drank 500mL water 30 minutes before a meal.
  • The control group imagined their stomach being full before the meal.

The water-drinking test group lost 1.3kg more on average than the control group.

The authors say these results indicate that water pre-loading before meals might lead to moderate weight loss.

How Drinking Water Affects Weight

Sure, when you ask “how does drinking water affect weight loss”, you’ll probably get a whole bunch of different answers.

But simply, the qualified studies show that drinking water can benefit weight loss in two main ways:

  1. It can help reduce calorie intake by 10 – 13% per day, when the water consumed replaces calorie-containing drinks.
  2. It curbs appetite when consumed before a meal.

Now over to you – if you were to put this into action, how many calorie-laden drinks in your diet could be replaced with plain water?

And what could remind you to drink water before a meal?

Let us know in the comments below!


Madjd, A.,  Taylor, M.A., Delavari, A, Malekzadeh, R,  Macdonald, I.A. and  Farshchi, H.R. (2015) Am J Clin Nutr December 2015 vol. 102 no. 6 1305-1312

Parretti, H. M., Aveyard, P., Blannin, A., Clifford, S. J., Coleman, S. J., Roalfe, A. and 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: 1785–1791. doi: 10.1002/oby.21167

Popkin BM, D’Anci KE, Rosenberg IH. (2010) Water, Hydration and Health. Nutrition reviews. 2010;68(8):439-458. doi:10.1111/j.1753-4887.2010.00304.x.

Melanie White

Melanie White

Chief Inspiration Coach

Melanie absolutely loves the art and science of picking apart habits and reconstructing them into more useful, pleasurable things.