A calorie is the unit used to measure the energy value of food and the energy used by the body to maintain normal functions. When the calories from food intake equal the calories of energy the body uses, weight remains constant. But when more calories are eaten than the body needs, the body stores those additional calories as fat, causing subsequent weight gain. One pound (1 lb) of fat represents about 3,500 excess calories.

Obesity is partially determined by a persons genetic makeup. If a child inherited the excessive body fat cells of his obese parents, more likely, he will tend to eat more than his body needs; thus, making him an obese too. Copying poor eating habits of parents also affects a childs body weight.

Lifestyles also play a key role in the triggering obesity. Eating big servings of food at restaurants and fast foods more frequently than nutritious home-cooked foods could help adding more calories and fats rather than limiting them. Devoting less time for exercise and other physical activities do not control weight gain.

Doing sedate recreational activities such as browsing the internet, video games, movies, and television, using labor saving devices such as personal computers, telephones, and remote controls, promote an inactive lifestyle. This is a potential risk factor for heart disease in later life.

Obesity is defined as being 20 percent or more above ones desirable weight range. It is a medical condition that refers mainly to storage of excess body fat. The human body naturally stores fat tissue under the skin and around organs and joints.

Fat is critical for good health because it is a source of energy when the body lacks natural energy necessary to sustain life processes, and it provides insulation and protection for internal organs. But the accumulation of too much fat in the body is associated with a variety of health problems.

Physical health can be measured through the appropriateness of a persons weight to his height; where the body weight refers to the measure of ones body mass, and the height is the measure of his tallness.

Body Mass Index is an accurate indicator of surplus body fat than kilos or pounds. It is a mathematical ratio of height to weight that can be linked with body composition (or body fat percentage) and with indices of health risk.

For instance, a woman measuring 5 ft high (1.52 m), with a medium body frame should weigh between 103 lbs to 115 lbs (46.72 kg 52.16 kg) to be considered healthy.

Another example: a man standing 5 ft 8 in (1.72 m) tall, with a large body frame is healthy if he is weighing between 144 lbs 163 lbs (65.32 kg 73.94 kg).

Otherwise, if their weight is lower than the desired body weight for their height, they are considered underweight, and if, in turn, their weight is higher than the desired body weight for their height, they are said to be overweight.

In the second part of this article I will discuss how you can determine your ideal body mass.