Sixty to seventy percent of your body is made up of water, so it's not surprising that daily weigh-ins reflect water-weight fluctuations; water-weight is a major component of what the scale measures, and the numbers can go up or down, depending on whether your body is losing or retaining water.

"But I don't want to drink more water - it puts my scale weight up!"

Ever made that comment before? Many people believe that drinking more water makes them weigh more because it causes water retention. However, drinking water actually helps to prevent water retention rather than cause it.

So if water doesn't cause water retention, what does?

Common causes of water retention include:

• Excess sodium/salt. The normal recommended daily maximum intake of sodium is 1500 mg. But just one teaspoon of salt supplies 2358 mg of sodium, and we often consume far more sodium than we need. This causes water retention and adds water-weight.

• Not drinking enough water. Although it sounds back-to-front, you need to drink a sufficient amount of water to flush out the water already in your body.

• Menstruation, constipation, and certain diseases such as heart and kidney disease may also cause water retention.

Water loss can also give you some false readings on the scale. Generally it's only possible to lose 1-2 pounds of actual fat per week, so if you're losing more than that you're probably losing water, not fat.

While you will always lose some water-weight when decreasing calories, some approaches to dieting can cause more water loss than others, resulting in false scale readings. For example:

• Excessive calorie restriction causes the body to use up stores of carbohydrates and to break down protein in the muscles. Since both carbohydrates and protein hold water in the cells, a loss of these also results in a net loss of water. As a result, rapid weight loss can often be made up of 75 percent water loss.

• High-protein or low-carb diets also cause water loss in the early stages. A high level of protein, especially from meat and dairy products, raises the levels of two toxic by-products - uric acid and urea. To flush these out, the body pumps lots of water through the kidneys and urinary tract.

• Diuretics can also cause water loss.