How does the body utilize fats during prolonged exercise?

During prolonged exercise, the body primarily utilizes fats by breaking them down into fatty acids for energy. This process is known as lipolysis, where triglycerides stored in adipose tissues are converted into free fatty acids and glycerol. The free fatty acids then enter the mitochondria of cells and undergo β-oxidation, producing ATP, which is the energy currency of the body.

This mechanism becomes particularly important during endurance activities, as the body's carbohydrate stores (glycogen) may become depleted. By relying on fat as a fuel source, the body can sustain energy levels over longer durations. Furthermore, the efficiency of fat oxidation increases with training, allowing trained athletes to rely more on fats during prolonged performances.

In contrast, converting fats into glucose is not a primary pathway since the body generally utilizes carbohydrates for quick energy needs. Additionally, while fat storage serves multiple roles, including energy reserve and insulation, it is not exclusively reserved for later use, as fats are actively mobilized during extended physical activity, rather than only stored. Lastly, fats are utilized not only during high-intensity exercise but also play a crucial role during lower-intensity and prolonged activities.