Weight Loss and Energy

Like a car, your body needs fuel to function. The diet must supply sufficient energy to support growth and development, maintain basic physiologic functions, meet the demands of muscle activity, and repair damage caused by illness or injury.

In the United States, energy intake and expenditure are measured in kilocalories, abbreviated as kcal, and commonly referred to as calories. Internationally the term is kilojoules, abbreviated as kJ (1 kcal = 4.184kJ). In this book, the terms energy and calories are used interchangeably to refer to the general concept of energy.

Body weight depends on physiologic controls of the balance between energy intake and energy expenditure. Weight increases when more energy is consumed than expended, overtime this imbalance can lead to obesity.

Until Einstein's equation E=mc�, which may also be written Calories=mc�, is invalidated the only way to reduce weight (m) is to reduce the amount of calories consumed (E). In other words, to lose weight it is necessary to eat less calories each day than you burn up, and the only way to gain weight is to eat, each day, more calories than you use. [Herbert, J., (Chief Hematology & Nutr. Lab.), Nutrition Cultism - Facts & Fictions , Bronx VA Medical Center, 1981]

The energy requirement of an individual has been defined as:

That level of energy intake from food which will balance energy expenditure when the individual has a body size and composition, and a level of physical activity, consistent with long-term good health; and which will allow for the maintenance of economically necessary and socially desirable physical activity. In children and lactating or pregnant women the energy requiremnet includes the energy associated with the depossition of tissues or the secretion of milk at rates consistent with good health (WHO, 1985).

If energy intake is consistently above or below a person's requirement, a change in body energy stores can be expected. If the imbalance between intake and expenditure continues over long periods, changes in body weight or body composition will occur and may adversely affect health.

Besides energy there are many nutrients that we require. They fall within two categories, Macronutrients and Micronutrients.

Macronutrients are carbohydrates, proteins and fats. Micronutrients include vitamins, minerals and water. Macronutrients primarily provide the body with energy, while Micronutrients do not provide any energy to the body.