Figure 1. Fuel Use During Exercise Varies as Exercise Intensity Changes. The relative contribution (% of energy expenditure) from carbohydrates predominates at higher exercise intensities. The higher the exercise intensity, the more carbohydrates are burned per minute. Additionally, the longer the exercise duration, the more the body relies on plasma glucose, leading to a higher overall contribution from carbohydrates. The amount of carbohydrates required will depend on the individual’s age, sex, body size 20, and fitness level.