Your body requires a certain amount of energy each day to carry out the essential functions you need to stay alive. When you exercise, your body requires more energy as you are using your muscles, lungs and heart far harder than when you are standing still or performing everyday activities.
Energy is not something that we can see, but we can see and feel its effects. Energy is produced when the molecule ATP (adenosine triphosphate) splits. The ATP molecule is made up of three components: a sugar molecule, ribose (the sugar that forms the basis of DNA), a base, adenine (a group of carbon and nitrogen atoms) and a three phosphate groups. ATP is produced in every cell in the body from the breakdown of carbohydrate, fat, protein and alcohol by various processes in the body.
Energy is produced when the ATP chemical bond splits: one of the phosphate groups breaks off, creating ADP (adenosine diphosphate) and AMP (adenosine monophosphate). This releases a lot of energy, which is used in exercise and given off as heat (approximately three quarters). When you rest, ADP and AMP are converted back to ATP and the energy production cycle continues.
The body stores only a limited amount of ATP, which is used up within a few seconds of beginning exercise. Therefore, your body needs to find an alternative source of fuel to convert into ATP. The alternative fuel is supplied by converting four items that we eat and drink.