The Katch-McArdle Formula is slightly different in that it calculates resting daily energy expenditure (RDEE), which takes lean body mass into account, something that neither the Mifflin-St Jeor nor the Harris-Benedict Equation does. The Mifflin-St Jeor Equation has been shown to be more accurate than the revised Harris-Benedict Equation. It was revised in 1984 to be more accurate and was used up until 1990, when the Mifflin-St Jeor Equation was introduced. The Harris-Benedict Equation was one of the earliest equations introduced. In most situations, the BMR is estimated with equations summarized from statistical data. The daily caloric need is the BMR value multiplied by a factor with a value between 1.2 and 1.9, depending on activity level. Basal metabolism is usually the largest component of a person's total caloric needs. An accurate BMR measurement requires that a person's sympathetic nervous system is inactive, which means the person must be completely rested. The BMR is measured under very restrictive circumstances while awake. Physical activity makes up ~20% of expenditure and ~10% is used for the digestion of food, also known as thermogenesis. For most people, upwards of ~70% of total energy (calories) burned each day is due to upkeep. In such a state, energy will be used only to maintain vital organs, which include the heart, lungs, kidneys, nervous system, intestines, liver, lungs, sex organs, muscles, and skin. It is the equivalent of figuring out how much gas an idle car consumes while parked. The basal metabolic rate (BMR) is the amount of energy needed while resting in a temperate environment when the digestive system is inactive. Related Body Fat Calculator | Calorie Calculator

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