Manuel Villacorta talks about metabolism:

What’s a metabolism?
Metabolism refers to your body’s ability to digest and utilize food energy (in calorie form) in order to maintain essential bodily functions like breathing and regulating heartbeats. “It’s the amount of calories that your body uses to make sure that it’s continually surviving,” Villacorta explains. One’s metabolic rate is determined by how quickly it can use up consumed calories, and that rate is affected by a variety of factors: age, weight, exercise, eating habits, and so forth. In order to condition our metabolisms to perform at peak levels, we must address each of these factors when coming up with a plan.

If you want to learn more about metabolism, read the entire article on DivineCaroline.com