“Fall” into Fitness: Your RMR Questions Answered
By Shelby Stoner, MS, PHASE IV Exercise Physiologist
Fall is officially upon us! With summer activities winding down, kids back in school, and the holidays approaching, now is as good a time as any to kick start your fitness routine! What better way to do so than see where you are currently at? At PHASE IV, we strongly believe in personalizing all nutrition and exercise programs to you and YOUR physiology, which is accomplished through scientific metabolic analyses known as Resting Metabolic Rate Testing (RMR) and VO2 Testing.
What is RMR?
Your Resting Metabolic Rate (RMR) is the number of calories used to maintain basic life functions such as brain activity, heart and lung function, tissue growth and repair, internal organ functions. It measures EXACTLY how many calories you will burn, without exercise, on a given day. Your RMR is the largest factor in determining overall metabolic rate and how many calories you need to maintain, lose or gain weight. Calories are burned by bodily processes such as respiration, the pumping of blood around the body and maintenance of body temperature while you are in a state of rest.
Your RMR can be responsible for burning up to 70% of the total calories expended, but this figure varies due to different factors. Your body will burn more calories in addition to the calories burned due to RMR. This is why there is a lifestyle factor (also known as Activities of Daily Living) that is included on top of your RMR. This factor accounts for functional activity like brushing your teeth, walking to your car, etc.
There are many other environmental and genetic factors that predict your RMR. Some of these factors include:
- Age
- RMR declines the older you get. After 20 years, Your RMR drops about 2% per decade. The cause of this decline is not clear. One reason may be due in part to a slowed metabolic rate of individual organs, such as the brain, liver, heart, and kidneys. Another cause may be a tendency for decline in physical activity and a sedentary lifestyle that leads to a decrease in lean mass (sarcopenia) and bone mineral density (osteopenia/osteoporosis).
- Gender
- Usually men have a greater muscle mass and a lower body fat percentage. Therefore, they have a higher RMR as muscle has more metabolic activity than fat.
- Body Composition
- The lower your body fat percentage, the higher your RMR (in most cases). For example, about 6 calories are burned per day for each pound of muscle that your body houses vs. 2 calories per day for each pound of fat that your body houses. In addition, after a significant weight loss, your RMR is decreased lower than expected relative to the change in body composition. Most researchers point to this as a key factor in the high rate of weight regain post significant weight loss. Identifying this post-diet RMR is a key step in long term weight loss success. It gives the information necessary to set an appropriate caloric goal for maintenance and teach a patient to eat within the constraints of their new metabolic requirements.
- Genetics
- Some people are born with faster metabolisms and some with slower metabolisms. Both the New England Journal of Medicine and the American Journal of Clinical Nutrition have published studies that examine the familial influence on variances in Resting Energy Expenditure. Both conclude that RMR is moderately heritable, and a low rate of energy expenditure may contribute to the trait of obesity in families.
- Nutrition
- Strict calorie reduction can decrease your RMR by up to 30%. You never want to fall below your RMR # because this will cause your body to store fat due to the fact that you are not feeding yourself enough just to sustain basic life function.
- Body Temperature/Health.
- Chemical reactions in the body take place more quickly at higher temperatures. For every increase of 0.5C in internal temperature of the body, the RMR increases by about 7%.
- External temperature.
- Your RMR increases with exposure to cold temperature. This happens because your body wants to generate the extra heat needed to maintain internal temperature. Prolonged exposure to heat can also increase your RMR.
- Glands
- An RMR-regulator called Thyroxin (produced by the thyroid gland) speeds up the metabolic activity of the body. An increase in thyroxin results in a higher RMR. When there is too much thyroxin produced (thyrotoxicosis) your RMR can increase by twice the amount. With too little thyroxin produced (myxoedema) your RMR may decrease to 30-40% of the predicted norm.
- Exercise
- Physical activity helps increase your RMR by increasing your lean body mass. Lean body mass (muscle) is more metabolically demanding vs. fat tissue.
How to determine your Resting Metabolic Rate (RMR)
The best way to determine what your resting metabolic rate is by performing the Resting Metabolic Rate Analysis (RMR). This the starting point for all science based nutritional programs for fat loss and achieving optimum body weight. The RMR is a 20-25 minute test that precisely measures your metabolic rate and tells you how many calories YOU burn throughout the day including the percentage of fats versus carbohydrates. The results tell you whether your body prefers to use fats as a main source of fuel or carbohydrates; everyone’s goal should be to be a “Better Butter Burner” and utilize your body’s ability to use fats as its primary fuel source, not just in exercise but throughout the day. With this information we arrive at how many calories you should eat a day to manage your weight and support your activities. This test will tell you if your metabolism is slow, normal, or fast and offers you basic guidelines on helping you shift your metabolism to reach your goal weight.
Interested in RMR Testing? Whether your goals are related to weight loss or improved performance, PHASE IV science has the answers. Call us to schedule a complimentary 30-minute health and fitness consultation at our facility in Santa Monica 310-582-8212 or email Shelby directly at shelby@phase-iv.net.
