Which of the following is classified as a fuel nutrient?

Fats are classified as a fuel nutrient because they serve as a primary source of energy for the body. When metabolized, fats provide more than double the energy compared to carbohydrates or proteins. This stored energy is particularly important during prolonged physical activity, as fats become a key energy source when carbohydrates are depleted. This efficient storage and release of energy make fats an essential component of a balanced diet for maintaining energy levels.

In the context of nutrients, vitamins and minerals play vital roles in metabolic processes, but they do not provide energy directly. Water is crucial for hydration and physiological functions, but it doesn't serve as a fuel nutrient either. Fats stand out among these choices because of their direct impact on energy provision in the body.