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%.

BMR factors 
 

• Muscle: Aerobic exercise like running or cycling has little effect on BMR. Weightlifting and other anaerobic exercises indirectly raise BMR by increasing muscle mass and resting energy use. More muscle mass means a higher BMR to maintain a person's physique at a given level.
• Age: The older and limber a person is, the lower their BMR, or minimum calorie intake required to support organ function.
• Hereditary features pass down BMR.
• Weather: Cold surroundings enhance BMR because of the energy needed to maintain body temperature. External heat might enhance BMR when the body expends energy to cool internal organs. BMR rises 7% for every 1.36°F increase in body temperature.
• Diet: Small, frequent meals enhance BMR. Hunger can reduce BMR by 30%. Similar to a phone that goes into a power-saving mode during the last 5% of its battery, a human body will compromise energy levels, moods, physical maintenance, and brain functions to more efficiently use the caloric energy being utilized to support it.
• Pregnancy: A distinct fetus raises BMR. Pregnant women consume more due to this. Depending on hormone changes, menopause can raise or lower BMR.
• Some vitamins or medicines raise BMR to aid in weight loss. Coffee is one.