Did you know that your body is made up of 50-75% water? That means if you weigh around 70kg, then roughly 43kg of you is water, most of which is found within our cells. It probably comes as no surprise then that water is vital to maintain good health and wellbeing. Poor water consumption is linked to dehydration, which can result in increased thirst, tiredness, poor concentration, headaches, dizziness and reduced exercise performance. So how much water are we meant to drink a day? Is eight glasses enough for all of us?

Why do we need water?

Water isn’t just needed to prevent you from becoming dehydrated or getting a throbbing headache. It is needed for every metabolic process in the body and has seven main functions.

  1. Transporting: Including nutrients, oxygen, messages to hormones and waster products
  2. Dissolving: Special proteins help carry molecules that can’t dissolve in water and these are transported in water
  3. Cleaning: Water helps flush out organs such as the kidney and liver that remove harmful toxins from our bodies
  4. Reacting: Water is part of most of the body’s chemical reactions. For example, water is part of the reaction involved when sugar (sucrose) is broken down into fructose and glucose.
  5. Lubricating: The lungs, joints and digestive tracts need water to provide lubrication for them to work properly.
  6. Padding: Water is a shock absorber. For example the vertebrae in your spine are layered between vertebral discs, which contain water, and allow you to bend.
  7. Regulating temperature.

What are the benefits of drinking more water?

Prevents health problems:

Increasing your water intake can assist in preventing headaches, constipation, lowering some types of cancers such as bladder and colorectal cancer, kidney stones and potentially acne.

Increased energy levels:

A 1.3% dehydration in females has been shown to lower mood and concentration levels, increase headache symptoms, increased perception of task difficulty.

Improved exercise performance:

Mild dehydration (1-3% body weight) caused by exercise or heat can negatively affect brain function and physical performance leading to reduced endurance.

Increased fat loss:

A small study involving 14 participants showed that drinking 2 litres of water in one day can increase energy expenditure by approximately 100 calories per day. Drinking water about half an hour before meals can also reduce the amount of calories consumed. Another study involving 48 middle-aged adults investigated whether drinking 500mL of water prior to each meal helped with weight loss. One group was assigned to a calorie controlled diet and the other was assigned to a calorie-controlled diet + 500mL of water prior to each meal. Weight loss was shown to be ~2kg greater in the water group compared to the non-water group.  Researchers believe this is because it reduces the amount of calories people end up consuming.

How much water should I drink per day?

Everybody’s water requirements vary depending on their age, body weight activity levels, environment, perspiration rate and health status. Thirst is a poor indicator of whether you have had enough to drink as you tend to stop feeling thirsty before your body is completely hydrated. The best indicator of whether you’re drinking enough is if you are passing pale yellow urine. If your pee looks like a council worker’s fluorescent yellow Visi-Vest, it’s time to rehydrate.

The average person also ‘eats’ their water from foods. Choosing fruits and vegetables with a higher water content such as carrots and apples is a great way to bump up your fluid intake, too.

Current national guidelines say men should aim for 3.4 litres per day of water, and women 2.8 litres. These recommendations should only be treated as a general guideline.

  • 1,500 – 2,000 mL/day (or 35-45 mL/kg/day) for adults
  • 1,000 – 1,500 mL/day for children
  • 500 ml of fluid on the night before exercise
  • 500 ml in the morning
  • 500 to 1000 ml, 1 hour before exercise
  • 250 to 500 ml, 20 minutes before exercise
  • 300 ml per 30 minutes of exercise

Take home message:

Water is essential for our health and wellbeing, and plays a role in exercise performance, cognitive function, digestive health and weight management. There is no additional health benefit to guzzling down lots and lots of water as you can only be hydrated to a certain level, after which you’ll just wee out any extra. Listen to your body and monitor your hydration status.


Armstrong, LE.,  Ganio, MS., Casa, DJ, Lee, EC., McDermott BP., Klau JF., Jimenez L., Le Bellego L., Chevillotte E., Lieberman HR. Mild dehydration affects mood in healthy young women. Journal of Nutrition. 2012. 142(2):382-8.

Daniel A. Judelson, DA., Maresh, CM., Anderson, JM., Armstrong, LE., Casa, JD., Kraemer, JW., Volek, JS. Does Fluid Balance Affect Strength, Power and High-Intensity Endurance? Sports Medicine.2007. 37 (10): 907-921

Gopinathan, PM, Pichan, G., Sharma, VM. Role of dehydration in heat stress-induced variations in mental performance. Archives of environmental health. 1998.43(10):15-17

Maughan, RJ. Impact of mild dehydration on wellness and on exercise performance. European Journal of Clinical Nutrition. 2003. 2: 9-23 

Dennis EA, Dengo AL, Comber DL, Flack KD, Salva J, Davy KP, Davy BM.2003. Water consumption increases weight loss during a hypocaloric diet intervention in middle-aged and older adults. Journal of Clinical Endocrinology and metabolism.88(12):6015-9.

Boschmann, M., Steiniger, J., Hille U, Tank J, Adams F, Sharma AM, Klaus S, Luft FC, Jordan J. Water-induced thermogenesis. Journal of Clinical Endocrinology and metabolism. 2003. 88 (12): 6015-19

Schoenfeld BJ, Aragon AA, Krieger WJ. 2015. Effects of meal frequency on weight loss and body composition: a meta-analysis. Nutrition Reviews. 73 (2): 69-82

Hall KD, Heymsfield SB, Kemnitz JW, et al. 2012. Energy balance and its components: implications for body weight regulation. American Journal Clinical Nutrition. 95:989–994

Thomas DM, Ciesla A, Levine JA, et al. A mathematical model of weight change with adaptation. Mathematical Biosciences Engineering. 6:873–887

Louis-Sylvestre J, Lluch A, Neant F, et al. Highlighting the positive impact of increasing feeding frequency on metabolism and weight management. Forum Nutrition. 56:126-128

Parks EJ, McCrory MA. 2005. What to eat and how often? American Journal Clinical Nutrition.81:3-4