Which statement about caffeine's effect on fat oxidation during exercise is supported by the material?

Which statement about caffeine's effect on fat oxidation during exercise is supported by the material?

• A. Caffeine decreases fat oxidation
• B. Caffeine increases fat oxidation
• C. Caffeine has no effect on fat oxidation
• D. Caffeine only affects carbohydrate metabolism

Answer: (B)

Caffeine tends to promote greater fat oxidation during submaximal exercise by increasing the mobilization and availability of fatty acids for use as fuel. It does this mainly through activating the sympathetic system: caffeine blocks adenosine receptors and raises circulating catecholamines, which increases cyclic AMP and stimulates hormone-sensitive lipase to break down stored triglycerides into free fatty acids. These free fatty acids then enter the muscle and are oxidized for energy, helping to spare glycogen. This effect is dose-dependent and most noticeable at moderate intensities and for longer-duration efforts, when fat oxidation contributes more to energy production. At very high intensities, carbohydrate metabolism dominates and the relative impact on fat oxidation is smaller, but the increase in fat availability still supports oxidation to some degree. Other options don’t fit because caffeine does not decrease fat oxidation, it does not have no effect, and it does not exclusively affect carbohydrate metabolism.

Caffeine tends to promote greater fat oxidation during submaximal exercise by increasing the mobilization and availability of fatty acids for use as fuel. It does this mainly through activating the sympathetic system: caffeine blocks adenosine receptors and raises circulating catecholamines, which increases cyclic AMP and stimulates hormone-sensitive lipase to break down stored triglycerides into free fatty acids. These free fatty acids then enter the muscle and are oxidized for energy, helping to spare glycogen.

This effect is dose-dependent and most noticeable at moderate intensities and for longer-duration efforts, when fat oxidation contributes more to energy production. At very high intensities, carbohydrate metabolism dominates and the relative impact on fat oxidation is smaller, but the increase in fat availability still supports oxidation to some degree.

Other options don’t fit because caffeine does not decrease fat oxidation, it does not have no effect, and it does not exclusively affect carbohydrate metabolism.