Slimming diets aim to reduce the amount of calories you eat, so you burn more energy than you take in, and therefore use more of your fat reserves. In the first week of a diet, water loss represents at least 70% of the weight loss. Low carbohydrate diets which reduce potatoes and bread lead to most water loss and leave you feeling tired and dehydrated. High protein diets are also not recommended. Your body converts excess protein into ammonia and organic acids and eliminates them through the urine, making your kidneys work overtime. Once you stop dieting your appetite may boomerang so that you eat more. Exercise is important to help preserve and protect your lean body tissue (muscles) while you are dieting. If you lose weight without exercise, about 25%-50% of the weight lost will be lean tissue, whatever diet you use.

A woman's natural stores of fat enable her to survive longer without food or even heat. When she becomes too thin and her body fat percentage falls too low, menstruation ceases and she will be infertile. But too much fat leads to poor health. Weight alone doesn't indicate whether you are too fat. Exercise physiologists use an implement called skinfold calipers to do an accurate 'pinch test' and determine the fat content of your body. The ideal body fat percentage is 23-25% for a woman and 15-17% for a man.

Eating brings higher levels of glucose in the blood which prompts the release of insulin, but it seems to take about 20 minutes from when you begin eating for your brain to register a feeling of fullness. Insulin enters the blood stream of a fat person slowly and this could be one reason why some overweight people eat more and for longer than the slim. This link between insulin and a feeling of fullness is one reason you should not eat quickly if you are slimming. Drinking something like unsweetened grapefruit juice, tea or coffee before a meal also has a 'turning down' effect on hunger, as does regular vigorous exercise.