What is the body's major source of energy?

Glucose is the body's major source of energy because it is a simple sugar that is readily utilized by most cells for metabolic processes. When carbohydrates are consumed, they are broken down into glucose, which can then be transported through the bloodstream to various tissues, where it is used in cellular respiration to produce adenosine triphosphate (ATP), the energy currency of the cell. This process is crucial for fueling all bodily functions, including muscle contraction, brain activity, and other vital processes.

In contrast, while fats and proteins can also provide energy, they are typically used in different metabolic contexts. Fats serve as a concentrated source of energy and are utilized primarily during prolonged exercise or fasting. Proteins, while they can be converted into glucose through gluconeogenesis when necessary, are predominantly used for growth, repair, and maintenance of body tissues, rather than as a primary energy source. Vitamins, on the other hand, are essential for various biochemical reactions but do not directly contribute to energy production. Thus, glucose stands out as the most direct and primary energy source for the body's needs.