Which energy source is primarily utilized during long-duration, moderate-intensity exercise?

During long-duration, moderate-intensity exercise, the body predominantly utilizes fats as its primary energy source. This is primarily due to the metabolic adaptations that occur during endurance activities. When the intensity of exercise is moderate, the body relies more on aerobic metabolism, where fats are oxidized in the presence of oxygen to produce ATP (adenosine triphosphate), the energy currency of cells.

Fats provide a greater yield of energy per gram compared to carbohydrates and proteins, which is particularly advantageous during prolonged activities. The body can tap into its vast fat stores, making it an efficient energy source for sustained efforts that last an extended period.

While carbohydrates are also important for energy during exercise, especially at higher intensities, their contribution diminishes as the exercise duration extends and intensity remains moderate. Proteins are not a primary energy source during exercise; they are typically utilized for muscle repair and growth rather than for immediate energy needs. Vitamins do not provide energy directly but are crucial for various metabolic processes.

Therefore, considering the efficiency and availability of energy substrates, fats emerge as the most significant energy source during long-duration, moderate-intensity exercise.