Metabolism: The Engine of Life

How Your Body Uses Energy

Metabolism is everything your body does to keep you alive and functioning. It’s how your body creates, uses, and stores energy from food. This ongoing process is called homeostasis—keeping your body in balance.

Food is fuel: Your body gets energy from food, measured in kilojoules (kJ) or calories.

• • Too much energy? Your body stores it as fat.

  • Use more energy? Your body burns it to power your cells and movement.

Two Sides of Metabolism: Catabolism & Anabolism

Metabolism has two key jobs that keep you strong, healthy, and energized:

Your body breaks down food (carbs, proteins, fats) into smaller building blocks. This releases energy to power your muscles, brain, and organs.

• Think of it like fueling a fire—your body takes food and turns it into energy.

Your body uses energy to build muscle, repair tissues, and support growth. This is how your body heals injuries, builds muscle after exercise, and keeps your cells healthy. Any extra nutrients not used for building get stored as fat for later use.

• Think of it like constructing a building—your body takes raw materials (nutrients) and uses energy to build and repair its structure. Just like a builder needs bricks, wood, and cement to construct walls and repair damage, your body needs proteins, fats, and carbohydrates to build muscle, heal injuries, and grow new cells.