The measure of the total energy utilized by the body to maintain its necessary processes while at rest. Those processes include keeping the heart, brain, and other organs functioning normally and the necessary replacement of old or damaged cells. About 75% of the food energy that we burn every day is used for these functions. The remaining energy is used to fuel physical work or is stored in fat reserves for when it is needed. Basal metabolic rate also refers to the minimum level of heat produced by the body at rest.