What does metabolism actually mean?

Your metabolism, scientifically speaking, is the rate at which your body uses energy at any given moment, or in other words, the rate at which your body burns calories no matter what you're doing, whether it be watching a movie or going for an afternoon run.

Metabolism is used in many contexts. For example, you've probably heard a friend say, "I have such a slow metabolism!" Most often when he says that, he means, his metabolism is resting. A resting metabolism is the calorie burn required to keep your body alive and moving. Your resting metabolism is always around, because even when you're sleeping, your body needs energy to keep your heart rate up, your kidney's functioning, etc.

So what does your resting metabolism account for? Normally, it accounts for 60 to 75 percent of your total calorie burn for the day. However, your active metabolism accounts for 15 to 30 percent which is totally dependent on how much you move around during the day. The thing about your body is that it always requires spending energy to do anything. So, even when you're eating and digesting your food, you're still burning calories, although not much, just 5 to 10 percent. Nevertheless, your resting metabolic rate is personalized, meaning everyone's rate is different. It depends on your body size, genetics, and your muscle mass.