This is your engine. Take care of it and it will take care of you!
By engine, I mean the heart and lungs make your body run. This is your cardiorespiratory system.
Your lungs need to rapidly breathe in large amount of air. Your heart needs to move blood to the lungs to pick up oxygen and get rid of carbon dioxide (gas exchange). Then your heart needs to pump that same blood all throughout your body to feed your cells. If you put the wrong kind of fuel into your blood, guess what it is spreading throughout your body!