How your body uses its fuel

By Dr Kelly

June 27, 2023

How we test your Metabolism in Green Bay

Metabolic Rate

Bioenergy testing can measure metabolic rate, which represents the rate at which the body converts fuel sources into energy. By analyzing oxygen consumption and carbon dioxide production, bioenergy testing can determine whether the body primarily relies on carbohydrates (glucose), fats (lipids), or a combination of both for energy production.

Respiratory Quotient (RQ)

Bioenergy testing calculates the respiratory quotient (RQ), which is the ratio of carbon dioxide produced to oxygen consumed during metabolism. RQ values provide information about the relative contribution of carbohydrates and fats to energy metabolism. An RQ closer to 1 indicates a greater reliance on carbohydrates, while an RQ closer to 0.7 suggests a greater reliance on fats.

Mitochondrial Function

Bioenergy testing can assess mitochondrial function, which plays a crucial role in energy production. Mitochondria metabolize glucose, fatty acids, and amino acids through processes such as glycolysis, beta-oxidation, and the citric acid cycle to generate ATP. Dysfunctional mitochondria may affect the body's ability to efficiently utilize different fuel sources for energy production.

Fuel Substrate Utilization

By analyzing metabolic parameters such as respiratory exchange ratio (RER) and substrate utilization rates, bioenergy testing can provide insights into how efficiently the body metabolizes carbohydrates, fats, and proteins. This information can help identify metabolic imbalances and guide personalized interventions, such as dietary modifications or targeted supplementation, to optimize fuel substrate utilization and energy metabolism.


At a cellular level, the ratios between oxygen and carbon dioxide will change based on what the body is burning and what it needs to get more energy. When you're walking on the treadmill, and if you get your heart rate up a little bit, more than likely you're burning fat. If you start running on the treadmill, you need more energy. The switch is going to happen. We're going to see the ratio change. You're going to start to burn more glucose, because you can get more energy from glucose than you can from fat. But fat is stable and steady and the older we get, we want to make sure we're efficiently burning fat to feel good and so that we don't just deposit fat. So it's all about the balance. When you're really working out hard, you become anaerobic. So those cells that are requiring a lot more energy, they go different route, an alternative route, lactic acid route as an example, because they can get more energy, at least temporarily.

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About the author

Dr. Kelly has 25 years of expert medical experience caring for the sickest of the sick people in critical care (including ICU, Heart surgery, Heart & Lung transplant surgery, as well as cardiology). She is a clinical specialist who has taken care of and trained others to care for the critically ill/the elderly and developed many screening and preventative programs to help improve the health of the population. The reality is that most people just don't have to be that sick. or stay that sick. So, Dr. Kelly decided to change the focus of the care she provided: to prevent, reverse and restore the health of individuals.

Dr. Kelly

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