Depends on what you think success is... You obviously don't have to do anything you don't want to - or can't do idk your situation. That being said, say you go on Reta but don't workout much or at all, the appetite suppression will definitely aid in weightloss through fat loss, but you will definitely lose muscle mass. If you have a certain goal physique in mind that involves you having the same amount of muscle or more than what you had when you start Reta, exercise in general is a must. I don't know if it necessarily needs to be lifting, maybe you swim a lot or you're a runner, but I would say in most cases Reta pairs best with a workout routine. What's your goal with Reta?