BMR is defined as the amount of energy that is required to exist and function. It is the defined “…as the energy required for performing vital body functions at rest, [and] is the largest contributor to energy expenditure.” BMR and the term resting metabolic rate (RMR) are often used interchangeably but they do differ slightly in the way they are measured. BMR will typically make up around 60-70% of calorie/energy expended during a day. ⠀⠀⠀⠀⠀⠀⠀⠀
Have you ever seen those online calculators that tell you your BMR? You enter your age, weight, gender and activity level and it gives you an estimate of how many calories you should eat each day. Well, forget about those calculators and only worry about what matters! ⠀⠀⠀⠀⠀⠀⠀⠀⠀ ⠀⠀⠀⠀⠀⠀⠀⠀⠀ ⠀⠀⠀⠀⠀⠀⠀⠀ ⠀⠀⠀⠀⠀⠀⠀⠀⠀ ⠀
BMR is affected by a number of factors, specifically the calories burned by a combination of the brain, heart, liver, kidneys, skeletal muscle, adipose tissue and residual mass (there is evidence that age and gender also play a role but that could be related to fat-free mass). Fat-free mass, which is everything other than adipose tissue and residual mass, is the largest determinant of resting energy expenditure (REE). The remainder comes from adipose tissue and residual mass (skin, stomach, intestines, glands, and lung tissue). The important question is which of the seven variables can we control? The answer is clearly skeletal muscle but fat is also modifiable (but in the other direction as decreased fat mass reduces the energy expenditure from fat). The total daily energy expended via these components can then be calculated as the sum of the following: skeletal muscle will burn 13kcal/kg/day and adipose tissue (fat) will counterintuitively burn around 4.5kcal/kg/day. Thus, the ideal way to burn more kcal/day thereby increasing BMR and reducing body fat over time, would be to increase skeletal muscle. This can be done through resistance training with a focus on muscle hypertrophy. ⠀⠀⠀⠀⠀⠀⠀⠀⠀ ⠀⠀⠀⠀⠀⠀⠀⠀⠀ ⠀⠀⠀⠀⠀⠀⠀⠀⠀