Question: Why can we survive without food but we can't survive without water?

Fiona Hatch answered on 13 Mar 2012:

Very interesting question. Personally I find that I really need lots of water to get through the day, sometimes I drink over 3 litres in one day!! Each person will differ depending on their body. This is because over 70% of the body is made up of water!! That’s a lot of water!!

Because of this, the body needs a constant intake (recommended 8 glasses a day) to keep that % up over 70%. If this starts going below 70% it can cause severe problems. If you imagine most of your body uses a lot of liquid. Your saliva in your mouth is constantly there ready for when you eat, that is made up of water (plus other things), your blood is liquid and is made up of a lot of water, when you sweat after playing sports, that is water (plus salt). So you have to keep all those by drinking lots of water. Our body also uses water to breakdown the food we eat. It helps us absorb different chemicals into our cells such as sugars. It keeps the blood moving round our body. Without water a lot of the processes that goes on in the body will not be possible.

On the other hand the body has a supply of food ready to use, this is known as fat. Everyone has some under their skin, just in case you do not eat enough, your body can break down the fat. If your body really needs energy (for example if you’re in a desert starving) then it can even break down your muscles and use those for food! But none of this is possible if you do not have water.