Why do I put on a two or three pounds a day and lose it again through the night

asks modge:
A. The reason for your weight changes is water. There is an amount of water in your system and it fluctuates over a 24-hour period.

Q. It can't weigh that much surely
A. You'd be surprised at just how much water weighs. One pint of water weighs a pound, or about half a kilo. So, if you drink a litre of water a day, you'll add a kilo or 2.2 pounds to your weight. It's a big change in weight and it happens pretty rapidly.

Q. So why do I lose weight overnight
A. There are a couple of things that cause a gradual loss of weight overnight. One is respiration. Every time you exhale you lose a little bit of water (you can see this work by breathing on to a cold piece of glass to see the amount of moisture you lose each time). The other way you lose water is through the skin - otherwise known as sweating. In just one night, you can lose a fair amount of water between the two of them. Add to that your first wee of the day which can lose another pound - about half a kilo - of water.

Q. Do I lose much water during the day
A. Yes. On average, a person will lose about 1.2 litres a day through urinating, as well as 1.5 litres because of perspiration and respiration. That makes a total of 2.7 kilos, or more than five pounds.

Q. Is that why it's important to drink water during the day
A. Yes. It's very important to drink enough water. If you are dehydrated it reduces your blood volume so less oxygen circulates around your body, and you will feel sluggish and thick-headed, and be less able to concentrate.

Q. How much water should I drink
A. You should aim to drink a 1.5 litre bottle of water a day - too much water can put a strain on your kidneys. Your food also has a moisture content, as do other drinks - although you should cut right back on fizzy drinks, tea, coffee and alcohol which can be dehydrating.

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By Sheena Miller