The basal metabolic rate (BMR) is the amount of energy needed at rest when the digestive system is quiescent. This is like calculating how much gas a parked automobile consumes. In this state, only the heart, lungs, kidneys, nervous system, intestines, liver, lungs, sex organs, muscles, and skin will function. For most people, 70% of daily energy (calories) is related to upkeep. Physical activity accounts for 20% of expenditures and digestion, or thermogenesis, for 10%.