The NEAT and exercise components have large variability and can greatly influence one’s total caloric expenditure. RMR and TEF are relatively constant, with minor fluctuations due to muscle mass and conditioning, and to dietary shifts, respectively. The total amount of calories an individual burns in a given day is known as total daily energy expenditure (TDEE) and it comes from several sources including RMR, the thermogenic effect of food (TEF), non-exercise activity thermogenesis (NEAT), excess post-exercise oxygen consumption (EPOC) and, of course, exercise (Ex). Thus, it is quite restrictive and only used in clinical or laboratory settings. Basal metabolic rate, however, can only be found during an awake, but totally rested and post-absorptive state, and in a neutrally temperate environment. The term basal metabolic rate (BMR) is often confused and/or interchanged with RMR or resting energy expenditure (REE). The rate at which these processes occur is measured in calories per unit of time, and is most often given in calories per day. Metabolic processes in the body require energy and are comprised of anabolic processes, which build up tissues, and catabolic processes, which break down tissues and fuel sources for energy. * Cunningham: RMR (This formula is similar to Katch-McArdle, but provides a slightly higher estimate.) Note that this result is significantly higher than the non-LBM formulas (i.e., revised Harris-Benedict and Mifflin-St Jeor equations). Therefore, using the Katch-McArdle equation: If our sample client has 10 percent body fat and weighs 80 kg, his LBM would be 72 kg (i.e., body weight of 80 kg – 10 percent body fat of 8 kg = 72 kg of LBM). To calculate LBM, multiple total body weight by body-fat percentage. A study (Johnstone et al., 2005) involving 150 adults in Scotland revealed that 62.3 percent of the variations seen in BMRs are related to fat-free mass (bone, tissue, muscle). These formulas should be used for more athletic clients, where muscle mass is significantly higher than average. Two formulas that consider lean body mass (LBM) include the Katch-McArdle equation (BMR) and the Cunningham equation (RMR). * A more accurate formula is the Mifflin-St Jeor Equation (calories/day): Weight in kilograms, height in centimeters, age in years * Revised Harris-Benedict BMR Equations (calories/day): Following are sample calculations for a 48-year-old man who is 180 cm (5’8”) and weighs 80 kg (176 lb) using several popular RMR equations.
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