The Energy Balance Equation

There is no mystery as to why we gain weight - it's a simple equation. We gain weight when the energy (calories) we consume exceeds the energy we use. In this situation, excess energy is stored on the body as fat. Eating just a small amount in excess of your needs will result in a slow but steady weight gain. Thus eating just 100 calories a day more than you need - the equivalent of 1 and a half digestive biscuits - will result in a weight gain of 4.7 kg/10 lb in a year.

To lose weight, you simply need to tip the balance so you use more calories than you consume, and your body will draw on fat reserves to provide the energy it needs. You can do this by restricting the number of calories you eat or by increasing the amount of calories you use, but without doubt the best way is a combination of diet and exercise.

Excerpt of Weight Loss Cooking For Health by Fiona Hunter