The primary source of energy for the human body is glucose, a simple sugar. Glucose is derived from the carbohydrates we consume, and it plays a vital role in our metabolism. Once ingested, carbohydrates are broken down into glucose through digestion, which then enters the bloodstream. From there, insulin helps transport glucose into cells, providing the necessary energy for cellular functions, physical activities, and overall body maintenance. While fats and proteins can also be used as energy sources, glucose is the body's preferred fuel, particularly for the brain, which relies heavily on it for optimal function.