The key differences between fats, carbs, and proteins lie in their biochemical structure and function within the body. Fats are energy-dense molecules that provide long-lasting energy and support cell structure and hormone production. Carbohydrates serve as the body's primary energy source, especially during high-intensity exercise, while proteins are crucial for building and repairing tissues, supporting immune function, and producing hormones. Each macronutrient plays an essential role in overall health, and understanding their differences helps individuals optimize their diets according to fitness and wellness goals.