The main energy source for the human body is glucose, a simple sugar derived from carbohydrates. When we consume food, our body metabolizes these carbohydrates into glucose, which then enters the bloodstream. Cells use glucose during cellular respiration to produce adenosine triphosphate (ATP), the energy currency of our cells. This process is crucial for powering all bodily functions, from muscle contractions to brain activity. While fats and proteins can also serve as energy sources, carbohydrates are preferred because they can be quickly utilized, making them essential for maintaining energy levels throughout the day.