But life depends on more than just the simple fact of metabolic activity. All foods have a Calorie equivalent which is the potential energy that that food is capable of producing. As you sit here quietly reading this your body is using energy to breathe, blink, swallow and keep your heart beating. Despite the anguish it sometimes causes, even thinking requires energy. In fact, in this quiet state your body requires approximately 80 calories per hour of energy.
Any activity increases the energy requirements of the body.
This is the metabolic rate - what your body does with the food in terms of how active you are. Many psychiatric drugs reduce the metabolic rate by 15 percent. The following example will show the effect of this. Anyone can tell you it is easier to prevent weight gain and maintain your weight than it is to gain it and have to lose it later. Approximately 10 percent of people taking lithium, especially after long term use, will also need supplemental thyroid medication.