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Metabolic Fuel Substrate Switching

Meaning

Metabolic Fuel Substrate Switching, or metabolic flexibility, is the physiological capacity of the body to efficiently and rapidly shift its primary energy source between carbohydrate (glucose) and fat (fatty acids) oxidation in response to changes in nutrient availability or energy demand. This dynamic adaptability is a hallmark of robust metabolic health and is essential for maintaining stable blood glucose levels and preventing chronic energy imbalance. Impaired switching is a core feature of insulin resistance and a sign of a narrow energy bandwidth.