Tag Archives: Body water

How much water do you really need each day?

12 Feb

I wrote a lengthy article about a month ago all about dehydration and the importance of water and its purpose in the human body, so I won’t repeat all of that here. What I do wish to revisit however is the section about the amount of water that the human body needs each day. The issue of hydration has been bothering me quite a lot ever since I started taking a serious interest in nutrition and fitness. With all of the varying opinions and the non-scientifically based advice out there, I decided to think about the issue to see if there was a way that I could create a reasonable definition as to the amount of water that the human body actually needs each day.

Now please bear in mind, I am no nutritional expert, I am not a scientist, nor do I have any conclusive evidence or peer-reviewed studies to present to you. What I am going to describe here are my thoughts and some calculations that I made to try to help me to create a better guide for myself and for my own understanding. If you find any of this information is useful to you then I would be very pleased if you could contact me with your own observations and experience. Please however don’t take any of the information that I have written here either as medical advice, nor as being entirely appropriate to your own individual health and well-being without first seeking the advice of your doctor.

In my previous water article I mentioned that I had been aiming to consume 1 litre of water per 22 Kg of bodyweight. Now, if I am working out hard every day, and I’m not prepared to carefully hydrate before, during and after each workout, then I suspect that this guideline would be easier to follow. When I am having a comparatively inactive day however, I find it hard to consume so much water. I just don’t find myself getting thirsty enough to trigger a need to drink nearly 3.5 litres of water given that most of the food that I consume these days also has a relatively high water content. It’s different when I am working out or the weather is very hot, but not during a rest day at relatively cool temperatures. So I got to thinking about what the minimum water would be that I would need in terms of the amount of water that my body would generally lose through ordinary metabolic processes.

Water losses occur through both digestion & sweating, and you also lose a substantial amount of water simply by breathing. Now, rather than attempting to catch all of the water that I use in a day, I decided to take a really basic mathematical approach, based on several assumptions:

  1. For the sake of simplicity, assume that water losses over time are linear. I’m certain that the body’s built in survival mechanisms would mean that water losses decrease over timet, but as it will make the math much easier and I am really shoddy at math I’ll stick with what I can do.
  2. Assume the average person can survive for 3 days without consuming any water given very little activity.
  3. Assume the average person reaches a point of fatal dehydration with 15% water losses.
  4. Assume the average person has a body water content of 57%. I.e.: a Water_Mass_Multiplier of 0.57.

Given these assumptions,

  1. Divide the 15% fatal water loss by 3 days, and you get a roughly estimated 5% water loss per day.I.e.: a Loss_Multiplier of 0.05.
  2. Take your body weight in kilograms (Mass) and multiply it by the Water_Mass_Multiplier to estimate the total Water_Volume in Litres.
  3. Multiply the Water_Volume by the Loss_Multiplier to estimate the Daily_Loss in Litres.
  4. Assuming I have an error in my formula, we’ll add a 10% error_correction_multiplier of 1.10 to ensure that we don’t completely underestimate the water requirement.
  5. Assuming the average person doesn’t sit completely still for an entire day, we’ll add a 25% loading which I’ll call an activity_multiplier of 1.25, to account for all of the mild activity that would increase the metabolic usage of body water.
  6. Assuming that all estimated losses are the daily water intake requirement, convert the result to get the estimated average mare minimum water requirement in millilitres per Kilogram of bodyweight.

So to make it all look easier to follow and more math like:


No matter what body weight I put into this formula, the DailyRequirement factor is always the same, which according to my very rough formula works out to be:

39 millilitres per Kilogram of body weight

So this  means that with all the hard work already done, all I need to do is take my bodyweight in kilograms (presently 76) and multiply it by 39 to get my personal minimum daily requirement of about 2900 ml.

But what about when you exercise, or if you live at a high altitude, or if the weather is hot? Well, As I mentioned earlier, other factors can affect your daily water consumption (including the water content of the food you eat), so it’s pretty clear that this formula and the daily requirement factor that I worked out is not going to suit every single situation. I would still suggest drinking at least 600ml about an hour both before and after a workout, and to be sure that you have water on hand during the workout to avoid dehydrating yourself through your exertions. This daily requirement factor is really something that I’ve worked out to give me a rough guide to ensure I avoid chronic mild dehydration and to ensure I am adequately hydrated throughout a normal and mildly active day. As always, I will continue to allow thirst to be a guide, and to monitor the colour of my urine which should always remain a “pale straw” colour. Any darker and I’m likely to be dehydrated, and lighter means I’m probably drinking more water than I strictly need. This shouldn’t be a problem however, as the body is very good as self regulating its water levels, and as I am spreading my water consumption across an entire day, the risk of water toxicity is basically non-existent.

I have personally been sticking to this new guideline for about a week now, and in that time I’ve noticed no difference physically as compared to when I was drinking the extra half litre per day, except that I find it less of a chore staying hydrated. My post workout recovery remains good, urine colour remains the same and I don’t have any of the dehydration symptoms that I used to get about 6 months ago, so I guess that backing off on the water slightly hasn’t been a problem.  I’ll keep monitoring how this goes, and I’ll update this formula as I learn more.

The thing that disappoints me though, is that I’m not sure if this formula is as applicable for people in the obese or severely underweight body mass categories. I know that fat cells don’t contain as much water as compared to muscle, yet the fat cells themselves still need to be maintained with access to body fluids, so it would make sense that having more body fat would still require more water. What I can’t figure out is how much, and I am not sure how much water a larger person feels compelled to consume. So what I’m saying is that I’m pretty sure that this formula works for me, but I’m not sure how useful it will be for people who are not of a statistically “average” weight. Given however that medications are applied based on body mass, I feel it would be reasonable to assume that taking a prescriptive approach to hydration would mean that a larger person could safely consume proportionally larger quantities of water, and that my rough formula would probably be applicable regardless… but I can be sure until I’ve had a chance to research this puzzle further.

As it is, I’ll continue to consume water according to my math and I’ll update the formula as I learn more. Interestingly enough I’ve just learned that if I convert my weight to pounds and use the half body weight in fluid ounces method, the amount of water I would consume is almost the same give or take a few ounces. So perhaps my logic isn’t so messed up after all! 🙂


Water: Critical for health, and weight loss

16 Jan

Those of you who’ve taken the time to read my “Who is this guy?” page would have learned that I have personally lived with clinical depression and anxiety. I was diagnosed, provided with access to counselling, given some medication and told that I would only ever come off the medication when I was “ready”. When I asked my doctor what depression is and how I got it, I was told about chemical changes in the brain, stress, anxiety, and that nobody really knows how people get depression. The psychologist I met gave me some great techniques to deal with both anxiety and depression, yet would not be drawn into a conversation that focussed on explanations when understanding how to deal with my moods was more important.

So what does a history of depression have to do with water or weight loss? Quite a lot as it turns out, and the more I examine my own experiences and how important both diet and exercise are to a person’s well being, the more I have come to believe that water may very well be at the centre of a great many health problems, and that understanding this importance may very well

On the Threshold of Eternity

On the Threshold of Eternity (Photo credit: Wikipedia)

help people to live better and healthier lives.

Back to my story for a moment. When depressed, it is not uncommon for a person to experience any or even all of the following symptoms:

  • Inability to concentrate
  • Confusion
  • Loss of appetite
  • Lethargy
  • Dry mouth
  • Insomnia
  • Irritability
  • Headaches
  • Dizziness when standing

Certainly these are all symptoms that I am very familiar with when depressed, and they are symptoms that can present for weeks, months, or even years. Did you know however that there is another condition that also expresses many of these symptoms, and that is Mild Dehydration.

Let’s talk about deydration

Mild dehydration is characterised as water losses from the body of between 1% and 2%, with any or all of the symptoms already mentioned, and also often accompanied by other physical symptoms, such as:

  • Abnormally dark and/or cloudy and/or acidic urine
  • A lack of tears when crying
  • Rapid heart rates
  • Constipation
  • Low stamina
  • Rapid onset of fatigue

Causes of dehydration can include diabetes, malnutrition, shock, burns, blood loss, vomiting, diarrhoea, drug/stimulant abuse, prolonged exposure to dry air, and even prolonged physical activity. There is one other most often overlooked cause for mild dehydration, and that is simply not consuming an adequate daily amount of water, and when I say water I really do mean just plain ordinary H2O, and not teas, coffees, carbonated|sport|energy drinks, or other “recreational beverages”, all of which can to varying degrees be diuretic – which basically means they cause you to pee more than you drink.
Now, I’m not going to suggest that chronic dehydration causes depression, but what if chronic dehydration is a symptom of a response to an emotional trauma, and that the combination of both trauma and dehydration are what causes the altered brain chemistry which is at the heart of a depressive disorder? I know that this is something I would really love some smart and nerdy science types to be looking into quite seriously. I couldn’t tell you if I’m the first to try and connect these concepts, but what I can tell you is that the idea isn’t as far fetched as you might think, given that as recently as 2009, the US Department of Agriculture‘s research division made a finding that Dehydration Affects Mood.

Ok… My brain and fingers have made a huge deductive leap, and I haven’t yet explained the stuff that I really intended this article to be about. Bear with me though, because I think that this does actually all link to health, fitness, and even weight loss.

Ok, so what about water?

Let’s look at the function of water in our bodies. Your body is roughly 57% water. Of that, approximately 2/3 of your body water is kept in your cells, and of the remaining 1/3 only 1/5 of that is in your blood stream as blood plasma. That remaining 4/5 of your water sits in your cellular tissue as interstitial fluid which acts to transfer water and nutrients between the blood stream and your cells. All in all it’s a complicated system of plumbing in which water plays a key role, but what is it that water really does for you? Quite a lot actually. In fact, your cells would not be able to function without water to act as a solvent to:

  • make essential nutrients small enough to pass into a cells
  • break down complex nutrients into simpler forms that the cells can use
  • create complex molecules from the waste that the cells produce

Chemical reactions within the cells generate heat, so water is also required to aid in heat regulation within the body. Water has a huge capacity to absorb heat, and this heat absorption effect works to stabilise body heat. To avoid overheating the heated water gets pumped around the body in the blood stream and is replaced by cooler water that has passed close to the skin layers of the body where some of the water is released as sweat which increases the cooling effect through evaporation.

The importance of water in this system becomes much more apparent when there isn’t enough of it to go around (aka dehydration), as this can effect the functioning of the body at a cellular level by reducing the efficiency of the system, preventing essential nutrients reaching the cells, and preventing heat and waste materials being removed from the cells. In extreme cases  cells can become so ineffective that they die, and if this happens on a large scale you’re in some serious trouble. So for such a simple and abundant chemical this H2O stuff is critical to our well being.

Given the importance of water in our bodies and how it affects cell functioning, water is therefore also critical to effective weight management, and in particular to weight loss. When we exercise our bodies generate more heat which makes the fats in our bodies more soluble. Digesting protein also increases body temperature in a less dramatic fashion but more importantly, when there is more protein to digest and not enough carbohydrate to go around, the body must turn to these dissolved fats to supply the nutrients that our cells need to do their thing. The more work your body does the more nutrient it uses up, and the more waste that is produced to eventually make it’s way to your kidneys and then out of your body in your urine. So in effect, with a good diet and exercise, you basically pee all of your fat out eventually.

Another thing is that fat cells retain very little water, almost nothing compared the to rest of your body tissue. The body also doesn’t retain more water than it needs to function efficiently, so if you drink a little more than you need you’ll simply end up flushing it out faster, which can be good for keeping your kidneys nice and clean.

Back to dehydration

Many people won’t even realise that they have become chronically dehydrated and may have been that way for years. How do you get this way? Simply by not drinking enough water to replenish the body’s daily losses. If you are getting headaches, or your sleep is messed up, or you feel drained of energy all of the time and your stamina is low, if you’re having trouble losing weight even though you believe your diet and exercise is fine, if you feel dizzy and like throwing up every time you exersize, if you’re constipated, grouchy, or even if your sex drive is all messed up, it’s entirely possible – and in many cases quite likely – that you are not drinking enough water each and every day.So if you’re in a state of mild dehydration, not only do you mess up the internal workings of your body at a cellular level, you also make it nearly impossible to effectively lose weight. The difficulty however is that sometimes we can confuse some of our thirst sensations with hunger, or with cravings for foods, often because the sensations can be very similar. Thirst is usually accompanied with a dry feeling in the mouth, yet sometimes the body can confuse the dryness such that the mouth waters and you think you’re experiencing the sensation of flavour instead of thirst. This can lead to a side effect where you start to put on weight, simply because you are consuming excess calories when the body is asking for water.

How much water do you need?

Every individual has different water requirements. The amount of water you should consume is affected by all sorts of things, such as climate, the amount of exercise you get, your physical size, whether you are taking medication, and so on. One thing that is quite clear is that the “8 x 8 oz glasses per day” rule only applies to someone who actually needs that amount of fluids. A small child would find it difficult to drink nearly 2 litres of water daily, whereas a large muscular athlete would become mildly dehydrated if limited to drinking that amount of water for too long. In general your thirst should guide you, however if you tend to eat when you are thirsty or if you regularly ignore your thirst, you’ll likely not drink enough during the day.

I have seen several recommendations on-line which vary from 20 to 45 litres of water per kilogram of bodyweight, and yet I haven’t seen any scientific evidence to back up any specific claim. For myself I tend to stick to approximately 1 litre of water  per 22 kilograms of bodyweight (which is approximately 34 fl oz per 49 lbs for the non-metrically-minded), in part because a little more water helps me to err on the side of caution and a little extra water spread through the day isn’t harmful, and also because it was suggested to me by a personal trainer several months ago as a good guideline for both weight loss, and recovery when exercising regularly.

People dealing with obesity might find this guideline difficult to follow however, given the disproportion between their total body fat and the smaller amounts of body tissues that actually need the water. Regardless of the recommendations and guidelines, if you have any doubts you should consult your physician and/or use the relative colour of your urine as a guide. Dark Yellow urine can indicate mild dehydration or could be an indicator of a renal problem. Very pale yellow (almost clear) would indicate you are maintaining your water requirement, and clear urine might indicate you could be overdoing it.

If you plan to exert yourself, spend a lot of time outdoors on a hot day, travel on a long distance flight,  work or exercise in a hot environment, or sit in a sauna, you should take the opportunity to hydrate yourself in the preceding 1 – 2 hours, consuming up to a litre of water over the course of each hour, and afterwards repeating the same hydration process to aid in your recovery.

A warning however is that it is no good drinking all of that water at once. Drinking too much water too quickly can lead to a condition called hyponatraemia, a word which literally means “low sodium in the blood” describing a condition which can be potentially fatal when the water itself behaves as a toxin and creates an electrolyte imbalance in the body. Spreading water consumption across an entire day is quite safe however, even if the total quantity consumed in a day is strictly more than your body might normally need.

A final word or two

I believe that maintaining your water levels is even more important than getting the rest of your diet or exercise perfect. The human body has an incredible capacity for self maintenance and in particular for healing. I have read that there are connections between several medical conditions and even mild dehydration, such as an increased risk of stroke and heart attack. If you wish to give yourself the greatest chance to reach your weight loss goal, perform at your peak both mentally and physically, and to give your body the best support to fight off disease and maintain yourself in the best of health, you really need to make understanding your water consumption a priority. If you get your water balance perfect for you, I believe that all the rest of your health goals will become so much easier to handle.

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