Almost any weight loss drug like that you gain it all back once you stop taking it. Makes sense though if you need to take a drug to loose weight you'd gain it back once stopping if you didn't make some serious lifestyle changes. I know a lot of people that have all lost a lot of weight taking that but none of them are changing their behavior otherwise. They will eventually suffer the consequences.
Personally I don't like the idea of weight loss drugs. While my goal wasn't weight loss back in may I made a decision to make healthier lifestyle choices, better eating and more physical activity and I've lost 35 pounds and now maintain this new weight. I'm not on any sort of restrictive diet. I made a series of small incremental changes that I would be able to sustain long term. Physical activities I enjoy and look forward too like walking, cycling, skiing, kayaking etc. Food wise I just cut back on the junk. I still enjoy junk food and take out, just now only a couple times a week and not everyday. I also started using a smaller plate at meal times to force me to take smaller more sensible portions and not the overladen buffet looking plate that American media portrays as the good life.
It helps I find if you can learn to like cooking. Then you can easily prepare lots of quick and healthy options that are tasty and cooked just the way you like.
There is no real secret formula. Healthy fit people lead healthy fit lifestyles.