Quantifying your metabolism with RMR

Did you know restrictive dieting and chronic stress can lower resting metabolic rate (RMR) up to 15 percent? Your metabolism is the total energy your body needs to maintain vital functions such as breathing. Three factors affect your daily energy expenditure:

RMR –  the number of calories you burn at rest

Physical activity

Thermogenesis – the amount of heat required by your body to process food

RMRis the most significant of these factors is RMR, which accounts for about 70% of your total energy expenditure. Oxygen consumption correlates with energy demand. Therefore, you can measure your RMR by knowing how much oxygen you consume every minute while at rest. As you need and use more oxygen, you need and use more energy. For example, think how you are out of breath while climbing up the stairs o doing any aerobic exercise. On average, each liter of oxygen correlates to about 4.82 calories of energy but estimations can vary by 30-40% off when calculated with a formula. In contrast, an RMR indirect calorimetry is the most accurate data. It can even predict what type of fuel your body are using for energy. This is done by dividing the volume of carbon dioxide produced by the volume of oxygen consumed. This is what the results look like:

What is VO2 Max?

It means your aerobic capacity. It’s the greatest amount of oxygen your body can pull from your blood when your heart is pumping its hardest. It is the best way to measure endurance, which depends on your body’s metabolism and ability to use oxygen. Other factors influence endurance such as height, weight, age, training, and genetics. Your VO2max is the precise amount of oxygen your body can use at your current level of endurance. The test translates this number into a target heart rate.

The test itself is simply exercising while wearing a heart rate strap and face mask and gradually increasing the intensity until the machine can calculate your VO2max.  

Are you a “fat burner” o “carb burner”?

The respiratory quotient (RQ) is the ratio CO2 production/O2 consumption. A RQ of 1 indicates you burn 100% carbs (CHO), while a general value of 0.7 indicates you burn 100% fats. The value ranges between 0.69 and 0.73, depending on the oxidized fatty acid carbon chain length. The average resting RQ of 0.82 thus reflects that the human body derives more than half of its energy from fatty acids and most of the rest from glucose. 

After the body’s needs during rest are met, additional energy is needed for diet-induced thermogenesis (DIT) and physical activity. DIT increases energy expenditure following food intake and is associated with the digestion, absorption and metabolism of food and nutrients. It accounts for 5-10% of TEE and is influenced by the amount and type of meal ingested. The measured thermogenesis of nutrients related to total calorie intake are 0-3% for fat, 5-10% for CHOs, and 20-30% for proteins, indicating that a high protein and/or CHO diet induces a greater thermic response compared to a high-fat diet. The reason for this difference is the higher energy cost of storing amino acids as protein and glucose as glycogen, compared to the cost of processing and storing fatty acids as fat. On average, an individual at rest can accommodate CHO intakes from 100-500 g/day, and fat intakes from 40-200 g/day, without displacing macronutrient stores if the total amount ingested does not exceed the subject’s energy requirements.

Leave a Reply