Somewhat surprisingly I find myself once again inspired to blog by an article in the economist.
The article, subtitled "A magic elixir is shown to promote weight loss" reported the results of a study in the US which found that a group drinking half a litre of water shortly before each meal lost 40 per cent more weight on a calories restricted diet than those who didn't.
I've long recommended drinking more water to aid weight loss, partly because hunger can often reflect thirst so by drinking more water you are likely to eat less calories. However the individuals in this study were given a set calorie intake and therefore this doesn't explain the extra weight loss.
Water is also an input into the chemical reaction that creates energy, and therefore burns calories, in the body. Therefore if your water intake isn't sufficient you can limit your ability to produce energy and lose weight.
I personally wouldn't recommend as much as half a litre just before eating as water can dilute your gastric juices interfering with the proper digestion of your food, but a glass of water 15 minutes before a meal is a good habit to get into, both to keep your energy levels up and your weight down.