I have known people that had good results and not good results.

Good results is the gastric band makes the stomach smaller and a person eats less food. They maintain or lose weight.

Not good results is the gastric band makes the stomach smaller and a person eats the same or more food. The stomach stretches and they gain weight. They cannot have the procedure again.

Personally, I wouldn't elect a gastric operation unless I had already gone on diet modification for a year. At that point I may not need a gastric operation. It is an invasive procedure and it does not guarantee weight loss. Eating less food is why it works. There are groups that help people maintain the discipline needed to eat less. I would try that first unless I am in a life threatening situation where it is medically required.

Here are other posts and articles about gastric operations.
Psych Central - Search results for Gastric bands for ed