I've always wondered about that - a gastric band is removable, right? Or is it?
But stapling the stomach actually reduces it in size and suddenly the patients can barely eat a side-dish full of food. So what happens when they reach their target weight? Move on to lots of fatty horrible stuff so that they don't waste away? Or eat every hour of the day?
Another thing affecting the obese - which is what has been my problem but in my case it was triggered by PCOS - is insulin-resistance. It's not quite type II diabetes (but it's on the way there), but basically the body starts to ignore the insulin, which is responsible for helping the body convert carbs and sugars etc into energy rather than fat.
It's ignoring it because the fat-laden body is going "Help! Metabolise away all this excess fat! Let's make tons of insulin to push it through!", while another system is going "Whoah horsey, too much insulin, I can't take it, talk to the hand, I ain't listening!" so instead of sugar and carbs turning into energy, it turns more readily to fat. Of course this leads to weight gain and a lack of energy so you can see how it can spiral out of control.
Obese people have been put on the medication I'm on (metformin), and unsurprisingly studies have shown some benefit, but that a strict diet/exercise reform is better - "Ooh a pill to help weight loss? Nice, don't need to exercise then! Another slice of cake? Yes please!" What's most dramatic is when the diet, exercise and metformin are combined, which is of course what I've done (though am lucky, I've found active hobbies I love doing and I work it into my daily commute), and that works very well.
Though I have to admit, I'm more likely to have some ice cream of a choc bar nowadays... Tsk...