Carbohydrates are one of the three main types of nutrients in food (along with proteins and fats) that give your body energy to move, think, and grow. When you eat bread, pasta, rice, fruits, or potatoes, you're eating carbohydrates. Your body breaks them down into a simple sugar called glucose, which powers everything from running around at recess to solving math problems.

Carbohydrates come in different forms. Simple carbohydrates, like the sugar in candy or fruit, break down quickly and give you fast energy. Complex carbohydrates, found in foods like oatmeal, whole wheat bread, and beans, take longer to digest and provide steady energy over time. Think of simple carbs as kindling that burns hot and fast, while complex carbs are like logs that keep a campfire going for hours.

Athletes often eat pasta or rice before competitions because carbohydrates fuel their muscles. Your brain also runs primarily on glucose from carbs: it uses about 20% of all the energy in your body, even though it only weighs about three pounds. That's why you might feel foggy or tired when you haven't eaten in a while.

Scientists use the word carbohydrate because these molecules contain carbon, hydrogen, and oxygen atoms.