This word describes the chemical activities that support life inside cells and organs. This includes converting food into energy — what we might think of as burning calories. But it also includes building important molecules like proteins and DNA and getting rid of waste products.
Metabolism isn’t just for warm-blooded animals like us. Everything living organism has one. Metabolism is what allows living things to grow, reproduce, move and more.
Often people mention metabolism when talking about bodyweight. They might say losing weight is hard because they have a “slow metabolism.” Or that they never gain weight because they have a “fast metabolism.” Whether or not that’s true, they are referring to only one specific part of metabolism — how fast the body processes calories from food. This influences how much we grow, yes. But there’s more to metabolism than that.
In a sentence
A person’s metabolism goes up and down throughout the day, burning different energy sources at different times.