How does the body's metabolism change during prolonged exercise?

During prolonged exercise, the body's metabolism undergoes significant adaptations primarily to sustain energy production and optimize performance. One key change is the shift from utilizing carbohydrates as the primary energy source to increasing the oxidation of fat.

Initially, during the early minutes of exercise, glycogen stores (derived from carbohydrates) are relied upon for quick energy. As the duration of exercise extends, especially past the one-hour mark, the body gradually increases reliance on fat as an energy source. This transition helps conserve glycogen stores, which are limited, thereby providing a more sustained energy supply over longer periods of activity. Fatty acids, derived from adipose tissue, are mobilized and utilized more efficiently, allowing for prolonged performance without depleting carbohydrate stores too quickly.

This metabolic adaptation is crucial for endurance activities, where conserving glycogen is necessary for maintaining exercise performance over time. Understanding this shift is important for athletes and individuals training for extended periods, as it can influence their dietary strategies and fuel management during exercise.