Carbohydrates are one of the body’s primary sources of energy and do provide calories — 4 per gram, to be exact — but they are not the unit used to measure energy. The correct term for the energy provided by food is calories. Carbohydrates are a type of nutrient, and they serve as the most immediate and easily accessible fuel for activities, especially high-intensity exercise and brain function. They come in various forms, from simple sugars to complex fibers. While carbs contribute to the total calorie count of a food, asking what measures that energy leads us to calories, not carbohydrates themselves.