Metabolism is the process by which your body converts food into energy and uses that energy to keep you alive and moving. Think of it like your body's engine: just as a car burns gasoline to run, your body breaks down the food you eat to power everything from breathing and thinking to running and growing.

Your metabolism works constantly, even when you're sleeping. It keeps your heart beating, your lungs breathing, your brain thinking, and your body at the right temperature. When people talk about having a fast metabolism, they mean their body burns through food energy quickly. Someone with a slow metabolism burns energy more gradually.

Different people have different metabolic rates, which is why some kids seem to eat constantly without gaining weight while others gain weight more easily. Your metabolism is affected by many things: your age, how much muscle you have (muscle burns more energy than fat), how active you are, and even your genes.

When doctors talk about metabolic disorders, they mean conditions where this energy conversion process in the body isn't working properly.