Why do carbohydrates, proteins, and fats provide energy?

Carbohydrates, proteins, and fats provide energy primarily because they are organic compounds composed of carbon, hydrogen, and oxygen. Organic compounds contain chemical bonds that release energy when metabolized by the body. Through the processes of digestion and metabolism, these macronutrients are broken down into simpler molecules which are then utilized in cellular respiration to produce ATP (adenosine triphosphate), the main energy currency in the body.

While the other options touch on characteristics of these macronutrients—such as their essential roles in diet or the complexity of their molecular structures—they do not directly explain why they are capable of providing energy. The ability to release energy during metabolism is fundamentally rooted in their organic nature and the presence of chemical energy within their molecular structure.