Resting Metabolic Rate: The Key to Understanding Your Metabolism

Knowing your individual resting metabolic rate (RMR) and what factors most influence your metabolism is essential in creating a smarter strategy to tackle weight loss, gain muscle, run longer or faster, taper before a race or refuel after training.

RMR represents the energy expended at rest to support basic physiological processes such as controlling body temperature, breathing, circulating blood and contracting muscles, as well as supporting brain, organ and nerve activity. RMR accounts for approximately 70% of the total energy we expend each day. Many factors influence your RMR such as age, body temperature, stress and muscle mass. Our RMR generally declines with increasing age due to a decrease in fat free mass and can increase due to stress.

The number of calories you need per day is dependent on a number of factors such as age, body weight, gender, RMR and physical activity levels. Your RMR may vary between 1200 and 2400 calories a day or more depending on your activity level. Once you know your resting metabolic rate you can determine your total daily caloric expenditure by taking into account the thermic effect of exercise (TEE) which is the amount of calories burned during exercise and the thermic effect of feeding (TEF) which is the amount of calories burned to digest food and accounts for less than 10% of your total caloric expenditure.

Learn more about the thermic effect of food and starvation mode from a previous blog, "The Meal Frequency Myth."
Learn more about the thermic effect of food and starvation mode from a previous blog, “The Meal Frequency Myth.”

Experts in Sports Performance at Houston Methodist see many people fall into the trap of eating too little when trying to lose weight which can have a negative effect on their metabolism and result in a significant slowdown of metabolism. The body thinks it is in starvation mode, making it harder to lose weight.

If you eat less than your resting metabolic rate or if you’re not eating enough calories to support your current activity level then you could be doing more harm than good to your metabolism. This is especially true for athletes. Once you find out your individual number you can determine exactly how many calories your body needs to lose, maintain or gain weight.

The opposite is also true as many people are eating way more calories than their body needs and are shocked when the results show that they need to be cutting their caloric intake in half or more. We recommend using a calorie tracker app that allows you to input your food intake and calculates your calories for the day.

RMR testing can tell you how many calories your body needs based on your goals, putting you in control of your weight rather than guessing. For accurate results, you should be fasted for at least eight hours and in a rested state at least 30 minutes prior to testing. Testing is best done first thing in the morning and involves breathing through a mask in a comfortable position for 20 minutes.

The test provides information on your metabolic rate and whether you are burning fats or carbohydrates. A nutritionist can use this information to tailor a diet plan specifically for you.