What is a calorie ?

If you read "The truth about dieting" you know that calorie restriction does not work. Dropping extra pounds is not a simple matter of eating less. It isn't the amount of calories you consume that makes a difference in terms of how much you weigh or how healthy you are.

A calorie is simply a unit of energy. It is defined as the quantity of energy required to raise the temperature of 1 gram of water by 1 degree centigrade at sea-level atmospheric pressure. We consume calories so that we will have something to burn. When calories are burned in a laboratory they are all equal and release the same amount of energy. Under these conditions a calorie is a calorie. But herein lays the problem. The calories you eat are absorbed at different rates and have different amounts of fibre, carbohydrates, protein, fat and nutrients – all of which translate into difference complex metabolic signals that control your weight and your health. It's called your 'metabolism'.

The conclusion here is that the kinds of calories you consume have a big impact on how much weight you gain because different types of food are metabolised in different ways. The type of food you eat directly affects what your genes tell your metabolism to do. This means that the type of calories you consume have a dual impact on the way you metabolise food (1) as a source of energy and (2) as a source of information or instructions to your genes that control your metabolism.