When you workout regularly, you typically gain muscle mass—or at the very least, maintain it. When you stop, it will decline. Why is this important? Well, muscle isn’t just important for strength or metabolism; it also impacts your energy levels. Here’s how: Muscle tissue is associated with having more mitochondria, which are considered the powerhouses of your cells. The more of these you have, the more energy your body can produce, and the more energy you feel.
Without muscle, you, inevitably, have fewer mitochondria, contributing to decreased energy levels.