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Can you Lose Weight by Drinking More Water?

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In order to achieve the body you want you have to train hard and eat well – if you’ve come here you’ve probably heard that water can help you to lose more weight.

But does the research back up the claims? In this article we’ll give you the low down.

Read on to learn more about:

  • The importance of H2O
  • Will drinking more water help you lose weight?
  • Can you drink too much?
  • Summary

The importance of water

Classified as an essential nutrient, H2O is needed in amounts higher than the body can produce it. Although figures change dependent on the source, it is estimated that this nutrient makes up 55-75% of your total body weight. Body water is higher in men than in women.

Dehydration of as little as 1% decrease in body weight can result in a number of physical and mental impairments. If dehydration reaches 3-5% then endurance and strength decrease [1]. Dehydration of >10% will cause more severe side effects such as delirium, confusion, rapid heart rate and breathing, or death.

Drinking it regularly has a number of benefits as is an important factor in a number body functions and processes such as digestion and gut health, temperature regulation, physical performance and concentration, and circulatory health.

It also provides hydration without calories – something that sweetened beverages do in excess.

It has been proposed that absolute increases in drinking water may promote weight loss by altering metabolism, and relative increases may promote weight loss by lowering total energy intake [2].

So can drinking more water help you can lose weight and speed up your fat loss? Let’s take a look at the key research:


Key Point: Water is an essential nutrient needed for a range of important bodily functions. Even slight dehydration can affect your physical and mental capacity.

Will drinking more water help me lose weight?

#Study 1: Boschmann [3]

This study, published in The Journal of Clinical Endocrinology and Metabolism investigated the effect of drinking 500ml of H2O on energy expenditure in 14 normal weight men and women.

Results showed that by drinking, metabolic rate increased by 30%, occurring within 10 minutes of ingestion – and peaked at around 30-40 minutes.

Interestingly though, whilst the increase in energy in men came from fat, in women it came from carbohydrates. 

The authors of the study suggested that by drinking 2 liters per day, energy expenditure could be increased by 400kJ/95kcal.

#Study 2: Davy et al [4]

In a similar study to that of Boschmann and colleagues, this study also used 500ml of water in order to measure energy intakes – this time though using 24 overweight or obese participants.

The volunteers were split into groups – those asked to drink water prior to a standardized breakfast, or those asked not to drink prior to the breakfast.

Results found that by drinking prior to the meal, energy intake was 13% lower, suggesting that habitual water consumption may assist in weight loss strategies in the overweight.

#Study 3: Dennis et al [5]

The purpose of this study was to determine if pre-meal H2O consumption increased weight loss in overweight and obese volunteers.

48 volunteers were assigned to one of 2 groups and studied over a 12 week period:

  • Group 1: low calorie diet and 500ml of water prior to each meal
  • Group 2: low calorie diet, no drink before a meal

At week 12, weight loss was 2kg higher in group 1 (44%). At the start of the study, energy intake from food was lower in group 1, but not at week 12.

Results suggested that consuming 500 ml prior to each main meal leads to greater weight loss than a hypocaloric diet alone.

#Study 4: Daniels et al [6]

This research is of particular interest as it is a review of all other research in the area of hydration and energy turnover.

In the study, the authors analysed all relevant research and concluded that water has a potentially important role to play in reducing energy intake, and consequently in obesity prevention.

One interesting aspect of the paper was the comparison of sugary drinks and water as pre-meal beverages – the results found that sugary drinks will cause a 7.8% increase in energy intake. This is a modest amount but still significant.

#Study 5: Stookey et al [2]

This study is an important one as it looked at the effects of drinking water over a long period – 12 months. It also looked at a large sample of volunteers – 173 overweight women.

The study saw the volunteers split into various diet and exercise groups, as well as various other interventions. What we are interested with here though is the effect of drinking more than 1 liter per day versus less than 1 liter.

The results of this study suggest that drinking more may promote weight loss for overweight women following weight loss diets with over 1 liter per day resulting in ∼2 kg or 5 lbs weight loss over 12 months. This equates to energy expenditure by ∼73 MJ (17,400 calories) or 2 kg of fat over the 12 month period.

can drinking water help you lose weight?

Key Point: Evidence suggests that drinking water prior to meals can reduce the amount of food you eat per meal

Can you drink too much water?

From the studies above it appears that aiming to drink water more is better for your weight loss goals. But be aware that you can drink too much – and that can be bad for your health too.

Hyponatremia is a condition where the sodium levels in your blood decrease – as an electrolyte we need sodium in order to regulate the amount of H2O in your cells and maintain bodily functions effectively.

Drinking too much too quickly – water intoxication – can induce hyponatremia. While aiming to drink 500ml prior to each meal is recommended, 5-6 liters in a short space of time for example will reduce sodium in the bloodstream far too much so more isn’t always better.

The symptoms of intoxication include restlessness, nausea, vomiting and headache. If symptoms are severe then it may well induce coma or even death.

Summary – can drinking more water help you lose weight?

Water is an essential nutrient needed for a range of important bodily functions. Even slight dehydration can affect these functions.

The evidence suggests that increasing short-term intake can translate into weight loss over a long-term period, with many studies showing positive differences. Drinking prior to meals can help you to control calorie intake, and over time can increase your metabolism.

Whilst these differences might only be modest, studies like the ones discussed above are all controlled, with other variables taken into account – in the real world of weight loss where your calories will more than likely be lower, and your food choices are healthier, weight loss may be higher.

Be aware that more is not always better – if you drink too much water, too quickly, you may experience symptoms of hyponatremia, – a condition where sodium is too low in the bloodstream.


  1. Sawka, MN et al. Effects of body water loss on physiological function and exercise performance. In: Gisolfi, CV et al eds. Fluid homeostasis during exercise. Carmel, Ind: Benchmark Press; 1990: 1-38
  2. Stookey, JD et al. Drinking Water Is Associated With Weight Loss in Overweight Dieting Women Independent of Diet and Activity. Obesity. 2012; 16(11): 2481–248
  3. Boschmann, M et al. Water-induced thermogenesis. J Clin Endocrinol Metab. 2003 Dec; 88(12): 6015-9
  4. Davy, BM et al. Water consumption reduces energy intake at a breakfast meal in obese in older adults. J AM Diet Assoc. 2008; 1087): 1236-9
  5. Dennis, EA et al. Water consumption increases weight loss during a hypocaloric diet intervention in middle-aged and older adults. Obesity (Silver Spring). 2010 Feb; 18(2): 300-7
  6. Daniels, MC et al. Impact of water intake on energy intake and weight status: a systematic review. Nutr Rev. 2010 Sep; 68(9):505-21.