How to Calculate and Improve Your Resting Metabolic Rate
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An individual’s metabolism (process of converting food into energy) can vary from day to day because there are a handful of internal and external processes involved in how much energy the body uses. An individual’s total daily energy expenditure is the sum of all the different processes:
- Thermal effect of exercise: (TEE): energy required for exercise or physical activity
- Thermal effect of food (TEF): energy required for eating, digesting, absorbing, etc.
- Resting metabolic rate (RMR): energy the body requires to function at rest
- Non-exercise activity thermogenesis (NEAT): energy required for daily living tasks (walking, standing, typing, etc.)
The resting metabolic rate typically contributes the largest percentage of calories used each day. If you can help your clients increase their resting metabolic rate, they will burn more calories, even while at rest. We’ll discuss resting metabolic rate, how you calculate it, and what you can do to help your clients increase it.
Resting Metabolic Rate
Resting metabolic rate is the number of calories (energy) that an individual burns at rest. Basal metabolic rate (BMR) is sometimes used interchangeably with resting metabolic rate; however, they are slightly different. BMR is the bare minimum energy required for the body’s basic functions at complete rest and is typically measured in a controlled or laboratory setting. BMR is measured in the morning to reduce any other variables that could affect it (stress, food in the system, etc.) (1).
Even a slight increase in the resting metabolic rate can contribute to weight loss over a period of time. For example, if a client’s RMR is increased by 75 calories per day, they will burn an extra 525 a week. That equates to over 2,000 calories each month and over 27,000 per year. Being that one pound of fat loss requires a deficit of 3,500 calories, the client could lose an additional 7-8 lbs. each year.
Calculating Resting Metabolic Rate
There are a handful of ways to calculate resting metabolic rate. However, it’s important to note that each of them has some level of error (2). But, if clients are looking for a baseline idea of their RMR, outside of a laboratory, they would use one of the following equations:
Harris-Benedict Equation (Revised)
One of the more common equations in the Harris-Benedict Equation. The original equation was created in the early 1900s and revised in 1984. Age, gender, height, and weight are needed for this equation.
Women: 447.593 + (9.247 × weight in kg) + (3.098 × height in cm) - (4.330 × age in years)
Men: 88.362 + (13.397 × weight in kg) + (4.799 × height in cm) - (5.677 × age in years)
Mifflin-St Jeor Formula
The 1984 revision of the Harris-Benedict equation was revised again in 1990 by Mifflin and St Joer. It is considered to be more accurate than the previous equations for calculating RMR (3).
Women: (10 x weight in kg) + ( 6.25 x height in cm) – (5 x age in years) – 161
Men: (10 x weight in kg) + (6.25 x height in cm) – (5 x age in years) + 5
Increasing Resting Metabolic Rate
There are a variety of different variables that contribute to an individual’s resting metabolic rate. Age, gender, and ethnicity may all be factors that play a role in an individual’s resting metabolic rate. However, age, gender, and ethnicity aren’t variables that can be controlled. And, although age and gender are often considered factors in an individual’s resisting metabolic rate, it is possible that amount of lean body mass is the main contributor because men typically have more lean mass (and higher RMRs) than women and lean mass typically decreases with age (decreased RMR with age) (1). One of the best ways to increase resting metabolic rate is by increasing muscle mass in the body, which is a variable that can be controlled.
Increase Muscle Mass
Muscle tissue burns more calories than fat tissue. So, the more muscle mass an individual has, the more calories they burn throughout the day, even while at rest. Because lean mass is the biggest contributor to resting metabolic rate, we are going to focus on the things your clients can do to help build more lean muscle tissue.
If your clients are looking to increase their lean muscle mass, strength training is one of the best ways to do it. Strength training can help shape the body, build muscle, and ultimately improve resting metabolic rate (4). Exercises that challenge the body beyond its current abilities are going to induce change. Since you want the muscles to grow to increase your clients’ resting metabolic rates you will want to focus on heavy weights, compound movements, and proper form. Although there may be some variance for every individual, hypertrophy training for many clients will look something like this:
Load: 67-85% 1RM
Rest: 30-90 sec (5)
High Intensity Interval Training (HIIT)
HIIT training is a form of interval training. It is short and intense bursts of effort followed by rest or lower intensity recovery periods. HIIT workouts are typically shorter in duration but intense and effective. HIIT training has shown to be effective in increasing muscle size in some individuals (6). More lean tissue will equate to a higher RMR.
Eat Calories and Protein
The body needs sufficient fuel to function and grow. Many clients, in an attempt to lose weight, will eat fewer calories. However, since the goal is to add more muscle to burn more body fat, the body needs adequate protein and extra calories to help build and repair the muscle. There is some variance in how many extra calories an individual needs; however, it is often recommended to start somewhere around 250 extra calories per day and make adjustments from there. Having a calorie surplus that is too high can contribute to fat gain.
The ideal recommended protein intake for muscle growth varies a bit as well. But, a good place to start is somewhere around 1.6-2.2 grams of protein per kilogram of weight each day (7)(8).
Understanding an individual’s resting metabolic rate is key to calculating their overall caloric needs and ultimately the key to determining caloric needs for weight loss or weight gain. To turn the body into a calorie-burning machine, lean muscle is the key.
Want to know more about how the body works so you can design effective programs for yourself and others? ISSA’s Certified Personal Trainer course can be completed from home at your pace. Get started today!
- McMurray, R. G., Soares, J., Caspersen, C. J., & McCurdy, T. (2014). “Examining variations of resting metabolic rate of adults: a public health perspective”. Medicine and science in sports and exercise, 46(7), 1352–1358.
- Frankenfield, D., et. al. (2003). “Validation of several established equations for resting metabolic rate in obese and nonobese people.” Journal of the American Dietetic Association, 103 (9): 1152-1159.
- Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, and Koh YO, (1990). “A new predictive equation for resting energy expenditure in healthy individuals.” The American Journal of Clinical Nutrition, 51(2):241-247.
- Lemmer, JT., et al. (2001) “Effect of strength training on resting metabolic rate and physical activity: age and gender comparisons”. Med Sci Sports Exerc, 33(4):532-541.
- Campos GE., et al. (2002) “Muscular adaptations in response to three different resistance-training regimens: specificity of repetition maximum training zones”. Eur J Appl Physiol.
- Blue MNM, Smith-Ryan AE, Trexler ET, Hirsch KR. (2018). “The effects of high intensity interval training on muscle size and quality in overweight and obese adults”. J Sci Med Sport, 21(2):207-212.
- Schoenfeld BJ, Aragon AA. (2018) “How much protein can the body use in a single meal for muscle-building? Implications for daily protein distribution”. J Int Soc Sports Nutr, 15:10.
- Phillips SM, Van Loon LJ. (2011) “Dietary protein for athletes: from requirements to optimum adaptation”. J Sports Sci, 29.
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