What is the primary source of fuel for the body during exercise?

The primary source of fuel for the body during exercise is carbohydrates. When a person engages in physical activity, especially at moderate to high intensities, carbohydrates provide a readily available source of energy. The body breaks down glucose from carbohydrates through a process called glycolysis, which can quickly supply ATP (adenosine triphosphate), the energy currency of the cell, to support muscle contractions.

Carbohydrates are stored in the muscles and liver as glycogen, which can be mobilized efficiently during exercise. The efficiency of carbohydrate metabolism makes it the preferred energy source for activities that require quick bursts of energy or sustained effort. While fats and proteins can also serve as energy sources, their utilization becomes more significant during lower-intensity activities and prolonged exercise, where carbohydrate stores might be depleted. Vitamins are crucial for various metabolic processes but do not directly serve as fuel for energy production during exercise.