Most obesity is due to poor nutrition and lack of exercise. Changing nutrition and exercising costs nothing and has numerous health benefits. Giving people an inferior, costly, and risky substitute for a simple and effective solution is not a good thing.
Exercising makes you fit, but unless you're an athlete it doesn't burn enough calories to make up for excessive calorie intake. I can usually burn 5-700 calories in an hour, but a Big Mac and 0.5 liter coke will undo that very easily and that's not counting the fries. You can subititute the burger with about 100 grams of potato chips or about three 0.5 liter beers. And if it's not excesses in sugar and fat you can easily overeat on quite ordinary food by simply eating too much.
You can easily overeat by 1000+ calories a day, in fact your body is built to quickly store fat in times of plenty since before refridgerators and preservatives that was the primary means of surviving harsh winters, draughts, bad luck hunting and so. The body is sending you all these wrong messages that you did great to secure all these reserves Except these days we only go up and never down.
Sure, it's just a matter of not eating but that's easier said than done, a nagging hunger is very very annoying. It's like I've grown up in a fairly cold climate, send a person from the tropical regions here and have him dress like me and I swear he'll think it's cold, damn cold. I doubt our bodies are that differntly build physically, but it's not as easy as to say it's all in your head. Maybe it is, but he's still freezing where I'm not. And I'm still hungry even though you're not. It's not fun. Being fat as fuck is also not fun, so I try balancing it out. But it's not easy.