UNIT 4 Fats Introduction to Fats 1. What Are Fats? Fats, also known as lipids, are essential macronutrients that provide energy, support cell growth, and help the body absorb fat-soluble vitamins (A, D, E, and K). They are composed of carbon (C), hydrogen (H), and oxygen (O) and are made up of fatty acids and glycerol. Fats are classified into different types based on their chemical structure and health effects.