Metabolic flexibility: myth or reality?

Longevity & Preventive Health Pillar

Your body should be able to switch easily between fuel sources: burning fat when you're fasting or at rest, then switching to carbohydrates when you eat or when the intensity increases. This ability to adapt has a name—metabolic flexibility—and it says a lot about your health.

An adaptation mechanism

The more efficiently your body burns what you consume rather than storing it, the more metabolically flexible you are. Conversely, when you lose that flexibility, problems arise: fat accumulates where it shouldn’t (in muscle and the liver), a phenomenon known as ectopic fat deposition, which fuels a vicious cycle.

The link to insulin resistance

Metabolic inflexibility is closely linked to insulin resistance—the inability of cells to take up and use ingested carbohydrates. The two reinforce each other and lie at the heart of a range of conditions: abdominal obesity, metabolic syndrome, type 2 diabetes, and cardiovascular disease. At the center of it all are chronic excess calories and dysfunction of the mitochondria, the cell’s powerhouses.

To understand where these mechanisms fit into the “oxygen chain,” see “Oxygen: The Ultimate Measure of Your Longevity.”

Measuring it through respiratory analysis

Metabolic flexibility can be quantified by the respiratory quotient (RER), which is calculated based on the carbon dioxide produced and the oxygen consumed, as measured by respiratory analysis (indirect calorimetry). An RER that struggles to decrease while fasting or to increase after a meal indicates a rigid metabolism—a condition often observed in people with insulin resistance.

The good news: she's recovering

Exercise—especially aerobic exercise—is one of the most effective ways to improve metabolic flexibility: it reduces insulin resistance and increases the muscles’ ability to oxidize fat. Combined with a diet that avoids chronic excess calories and ultra-processed foods, it is the best strategy for regaining this flexibility—an area where kinesiology excels.

References

Goodpaster B.H., Sparks L.M. “Metabolic Flexibility in Health and Disease.” Cell Metabolism. 2017;25(5):1027-1036.

Curious to find out if your metabolism is flexible? Book your metabolic analysis →

This article is provided for educational purposes only and does not constitute medical advice. If you have any health conditions, consult a doctor before starting to exercise.