The body prioritizes carbohydrates over lipids for energy because carbohydrates are simpler molecules that can be quickly converted into glucose, making them readily available for immediate energy needs. Lipids serve primarily as energy stores, insulation, and protection, and are utilized for energy only when carbohydrate supplies are low. In vertebrate muscles, fatty acids can be respired similarly to glucose, but this process occurs after carbohydrate stores are depleted. The quick breakdown of carbohydrates by enzymes like glucagon allows for efficient energy use, reinforcing their role as the primary energy source for the body.