FAQ - What percentage of body fat is water, if any?

Q) What percentage of body fat is water, if any? A friend of mine insists that if we can compress the body fat that it will "melt" away and then we urinate it out. Please provide references to support your answer. Thanks.

A) The best way to look at this is to start with a whole body.

Let's take an average (70kg) male. He will be made up of approximately 42kg of water; 12kg of fat; 12 kg of protein and 4 kg of bone/minerals. This makes his total body water content approximately 60% and his total body fat approximately 17% (water and fat being the two you're interested in).

(The World Health Organisation healthy body composition tables say that a 20-40 year old man should have 8-19% body fat and a 40-60 year old man should have a 11-22% body fat. (Women should have 21-33% body fat when they are aged between 20-40 and 23-35% between 40 and 60). So, our chap, at 70kg and 17% body fat is normal and healthy.)

Your question is interesting because it gets to the next level of - where is the water? Hanging on to the fact that our average man is 60% water, different parts of the body have very different water compositions. Blood, for example, is approximately 83% water. Body fat can be as low as 10% water. But all this water added together still adds up to the whole 60%.

So, yes, there is water in body fat - approximately 10% - but there is way more water everywhere else in the body. Here's a few other things that may be interesting (as your question is quite broad):

1) I just don't see how your friend thinks you can compress body fat! Are you planning to squash each other or something?! An apple is probably 90% water and, even if you smash it with a hammer, you won't get all the water out! The way to get the water out would be to apply heat (e.g. boil the apple, a person sits in a sauna) and then you will lose water from all over the body.

2) You don't want to lose water - as soon as a person loses just 2.5% of their body weight from water loss, they lose 25% of their physical and mental abilities and efficiency. For our example man this would only takes just two litres of water to be lost.

3) At the 'whole body' level, the more fat a person has, the lower the percentage of water in their body i.e. the percentage of body weight that is water varies inversely with body fat. This explains why women have a higher fat content than men and a lower water % and why obese people have a lower water % than normal weight people. You don't want to lower your water % therefore (which is what urination is the end result of). You probably want to lower your fat %.

4) If the end goal of all this is to lose weight, you can lose water weight very quickly by crash-dieting (not good), as the body will use up its stores of glycogen to keep you going and glycogen holds a lot of water with it. As soon as you eat normally again, you'll put all the glycogen back in the storage room and the water goes back with it.

5) To lose fat, I don't subscribe to the calorie theory (create a deficit of 3500 calories to lose 1lb). I think eating less just makes you want to eat more, makes you store fat and slows your metabolism. Just eat nothing but real food for as long as you need to lose weight (meat, fish, eggs, dairy products, vegetables, salads, fruit, brown rice and not much else) and you can't go far wrong.

Hope this helps! Zoe

Zoe Harcombe: The Harcombe Diet