Which of the following describes the effects of caffeine on metabolism?

Caffeine plays a significant role in enhancing metabolism, primarily by stimulating energy expenditure through the nervous system. It acts as a central nervous system stimulant, which can increase alertness and reduce the perception of effort during physical activity. This stimulation can lead to an increase in metabolic rate, enhancing the body's capacity to burn calories.

Caffeine also promotes the release of catecholamines, such as adrenaline, which facilitates lipolysis—the breakdown of fat stores for energy. Through these mechanisms, caffeine not only boosts energy expenditure but also can improve physical performance due to its ability to help mobilize fatty acids from adipose tissue.

In summary, option C is correct because caffeine indeed stimulates energy expenditure via its effects on the nervous system, contributing to an increase in overall metabolic activity and potentially aiding in weight management and performance enhancement.