Understanding your metabolism

by Jackie Dorman — 

Metabolism, or more specifically resting metabolism (RMR), controls how many calories the body burns at rest.

These calories are the measure of energy used by highly active tissues, such as the heart, brain, kidneys, liver and gastrointestinal tract, to keep the body’s internal activities functioning.

For most people, RMR (resting metabolic rate) accounts for 75 percent of the total calories expended in a day. The remaining 25 percent fuels physical activity and provides energy for the digestion and absorption of food.

A general formula can be used to estimate RMR, based on gender and weight. For men, the formula is: one calorie times body weight in kilograms times 24 hours. For women, the formula is: 0.9 calorie times body weight in kilograms times 24 hours.

Additional factors, such as the amount of muscle tissue, growth periods, fluctuations in body temperature and hormones, can directly influence RMR. Any one of these factors can dramatically increase or decrease metabolic rate, and should be remembered when basing RMR values on a general calculation.

Considering the numerous factors that play a role in metabolism, select health and fitness centers now offer a more individualized approach to calculating RMR. With the use of portable metabolic testing carts, measurements of oxygen input versus output determine exactly what is happening inside the body. This type of metabolic test identifies your unique resting metabolic rate.

Once you determine your true metabolism, food intake can be adjusted to balance your body’s needs with your weight-loss goals. Understanding your RMR can help identify your target caloric zones, determining the maximum number of calories you can eat and still lose weight safely and effectively.

Caloric adjustments should be made by reducing food intake and increasing physical activity. Keep in mind that too few calories can cause you to lose muscle tissue, deprive you of vital nutrients and actually slow your metabolism.

Unlocking the mystery of your own metabolism is the key to losing weight and keeping it off. Contact your local health and fitness center to see if metabolic testing is available. Find out if it is truly a slow metabolism that is weighing you down.

Jackie Dorman, BS Athletic Training, ATC/L, CSCS NPTI-CPT/Instructor at Troon Mountain Health and Fitness. 480-538-2877, Jackie@troonmountainfitness.com or www.troonmountainfitness.com. 

Reprinted from AzNetNews, Volume 25, Number 6, December 2006/January 2007.