This comes from The Power of Habit, by Charles Duhigg: “Take, for instance, studies from the past decade examining the impacts of exercise on daily routines. When people start habitually exercising, even as infrequently as once a week (emphasis added by me), they start changing other, unrelated patterns in their lives, often unknowingly. Typically, people who exercise start eating better and becoming more productive at work. They smoke less and show more patience with colleagues and family. They use their credit cards less frequently and say they fell less stressed. It’s not completely clear why. But for many people, exercise is a keystone habit that triggers widespread change. ‘Exercise spills over,’ said James Prochaska, a University of Rhode Island researcher. ‘There’s something about it that makes other good habits easier.'” If that’s not convincing enough to get you off the couch and over to the gym, I don’t know what else to say!
