Your body prefers carbohydrates, when it comes to higher intensity exercise

Your body has its preference when it comes to fuel for energy. Whenever exercise intensity increases from low to high, the body switches to glucose and glycogen as the main source of ATP. Metabolically more energy is created in the mitochondria (ATP) due to the aerobic breakdown of carbs compared to fat. As exercise intensity increases, fast twitch muscle fibers come into play (because of their enzymes). This makes them better equipped to use carbohydrates for ATP production. Keep in mind that higher-intensity exercise will also produce epinephrine production, thus increasing the metabolization of carbohydrates. And for those who are not familiar with fast twitch and slow twitch muscle fibers. Fast twitch muscle fibers come into play with higher intensity activities and some people may have a genetic make up where they have more fast twitch muscle fibers. For instance bodybuilders may have a higher amount of fast twitch muscle fibers. Compared to long distant runners who may have a greater amount of slow twitch muscle fibers.