Human metabolism is the sum of all the chemical reactions that occur in your body. Your body takes in foods, burns some to generate power, uses some to produce new material, and routes the rest into storage for future use. The chemical reactions that occur either break down large compounds into smaller units (the foods you eat, for example, are broken down into smaller units of energy), or build complex structures from smaller units (your muscles are made up of fragments that come from the protein foods you eat, like eggs). Human metabolism is the sum total of all the reactions needed to keep your body alive and moving. The energy required to make all this happen, can be translated into the calories you need each day.
Approximately 60% to 75% of your daily calories are used just to keep you alive. Energy is needed to maintain your body’s temperature, allow your nerves to work, let you breathe, keep your heart beating, allow your organs to function, nourish your body tissues, and repair and replace body fluids and parts. It’s a big job and it goes on 24 hours a day.
