 A balanced diet combined with regular exercise aid in the overall general health of the body.  Humans require energy to function. The total energy used by an individual depends on the type and intensity of the activity and the energy required for basic life processes

 The amount of energy required to maintain minimum essential life functions is called basal metabolic rate, or BMR.  Humans obtain the energy required to carry out basic life processes from the food they consume.

 Food energy is measured in calories.  The amount of food energy (calories) a person requires varies with body weight, age, gender, activity level, and natural body efficiency.  For the body to use food (proteins, lipids, carbohydrates) for energy and building materials, the food must first be digested into molecules that are absorbed and transported to cells.

 Metabolism is the set of chemical reactions involved in storing fuel (food) molecules and converting fuel (food) molecules into energy.  In order for the body to use the fuel energy stored in food, the food must first be digested and combined with oxygen (oxidized).

 Three factors contribute to the overall metabolic rate of the body.  The Basal Metabolic Rate (BMR) accounts for about 60% of all energy used by the body.  Daily physical activities such as walking and moving around account for another 30% of the energy used by the body.  Finally, 10% of the energy used by the body is used to digest and process (oxidize) food.

 If one consumes more calories than the body uses, the excess is stored and weight is gained.  Weight loss occurs when fewer calories are taken in than the body needs.

 To burn food for the release of energy stored in it, oxygen must be supplied to cells, and carbon dioxide removed.  The heart /lung system work together to deliver oxygen rich blood to all of the organs, tissues and cells of the body.  Lungs take in oxygen for the combustion of food and they eliminate the carbon dioxide produced.  The circulatory system moves all these substances to or from cells where they are needed or produced, responding to changing demands.

 In order for systems to work properly, energy from the cells must be transformed into a useable form for cells and ultimately, organs, to perform work. These systems work together in order for the body to function properly and maintain a balance.  Regular exercise is important to maintain a healthy heart/lung system, good muscle tone, and bone strength.  Regular exercise increases the heart rate providing more oxygen for the body to use for processing food. A healthy body requires a delicate balance between a healthy diet and physical activity.

 In order for energy balance to occur, Energy In = Energy Out. This means that caloric intake equals caloric output.  Food components (protein, fat, and carbohydrates) taken into the body have the following fates: they can be used to fuel metabolic activities and physical activities, they can be incorporated into growing body tissues, and they can be stored as fat.

 There are two important concepts of energy balance  First, to allow for normal body growth, more food energy must be consumed than can be accounted for solely on the basis of energy required for metabolic and physical activities.  Second, insufficient energy intake may affect cellular metabolic activities, body weight, growth, tissue formation, and health.