People obviously lose a lot of weight when they exercise. After a period of rest, their weight increased significantly. Why?
I don't think you have been exercising. If you insist on exercising, you won't develop it for a while, except for your health, because everyone who insists on exercising knows that once exercise forms your habit, you will feel uncomfortable if you don't exercise for two days. You just don't insist and lose to inertia.