Which three nutrient classes are known to supply energy?

The correct answer highlights the three nutrient classes known for supplying energy: fats, carbohydrates, and proteins.

Fats are energy-dense macronutrients, providing about 9 calories per gram. They serve not only as a major source of energy but also play a critical role in hormone production, absorption of fat-soluble vitamins, and cellular structure.

Carbohydrates are the body's preferred energy source, particularly for the brain and during physical exercise. They yield about 4 calories per gram and are broken down into glucose, which is used immediately for energy or stored as glycogen in the liver and muscles for later use.

Proteins, while primarily known for their role in building and repairing tissues, can also provide energy. They are less efficient than carbohydrates and fats for energy purposes, yielding about 4 calories per gram when glucose is unavailable.

Other options include nutrients that do not provide energy, such as vitamins and minerals, which are critical for various metabolic processes but do not contain calories. Fiber, while essential for digestive health, also does not provide energy in the form of calories. Thus, the choice of fats, carbohydrates, and proteins accurately represents the nutrients that supply energy to the body.