It's true that aging can affect energy level—and your metabolism. But it doesn't control it. In fact, a lot of what seems to be age-related energy loss is really about changes in your lifestyle. Obviously, if you've traded in long Sunday strolls for minivan driving to and from soccer games, then that—more than your age—is probably to blame.
Try This: Move more, not less. Even if it's making an effort to fidget more, there will be benefits. "Just being restless—standing, pacing, toe tapping—can burn about 350 calories a day," says sports and exercise consultant Greg Chertok. And all of that movement will get you energized; it won't make you more tired.