During the process of the biochemical reaction, the carbon and oxygen combine to form carbon dioxide gas. In order for metabolism to occur a person must breathe. The Human Metabolism Laboratory takes advantage of this fact. An instrument in the laboratory measures the amount of CO 2 gas exhaled by the subject. Because metabolism and CO 2 gas production are directly related, the instrument can calculate the rate of metabolism by the subject.
Metabolism is the conversion of energy in food to energy in the body.
If energy in food is not used for work or processes, then the body stores the excess energy as fat. Resting energy expenditure is called the basal metabolic rate, but most people don't rest all day so the basal rate must be multiplied by a factor. The following factors can be used. The result of the principle of conservation of energy is that a person becomes fat if the caloric intake exceeds the energy expenditure for a long period of time. Thus, the person is overweight but not at risk for obesity related health problems.