What type of exercise utilizes the highest percentage of fat for energy?

Slow long-distance activities are known to utilize a higher percentage of fat for energy because they occur at a low intensity over an extended duration. During such activities, the body's demand for energy can be met efficiently through fat oxidation, which serves as a primary fuel source when carbohydrates are not in high demand. This is particularly true as the body has a greater capacity to mobilize and metabolize fat when engaging in prolonged, steady-state aerobic activities, allowing for sustained energy output.

In contrast, high-intensity interval training and resistance training primarily rely on carbohydrates due to their energy demands, which require quick bursts of energy that fat oxidation cannot meet efficiently. Medium-intensity aerobic exercise does use fat, but not as predominantly as slow long-distance activities, where fat becomes the main fuel source as glycogen stores are not depleted rapidly. Thus, slow long-distance activities stand out for their capability to utilize fat as a significant energy source, especially in endurance scenarios.