The risks of gastric bypass surgery are tremendous, especially given that to qualify for the surgery you have to be 100 pounds or more over your ideal weight. I would have qualified for it 2 years ago.
Once the surgery is over, you're still not out of the woods. Many people have ongoing health problems afterwards, including nausea, vomiting, diarrhea and malnutrition. Basically, it's weight loss through starvation, and guess what that does to your metabolism, not to mention your lean body mass. Life is never "normal" for these people again. Even if the bypass is later reversed, they will have a lowered metabolism and have to live on very few calories for the rest of their lives or risk regaining the weight. Then there's the psychological aspects of all of it; a lot of people just can't handle losing that much weight that quickly psychologically, nor can the people in their lives; it has resulted in divorces and broken friendships galore. Think about it...if you were using your fat to hind behind and feel "safe" what happens when that "shield" is gone? What do you do then?
People who lose weight through WLS often require plastic surgery to deal with the excess skin that resuts. I'd rather not have my weight loss result in several scars and even more self-image issues to deal with.
This truly is a last ditch effort and it's unfortunate and sad that many are using it as their first resort instead of the last one. OTOH, many people who undergo this procedure honestly believe that it is their only chance to get the weight off and save their lives; if you had tried conventional diets and failed and your doctor told you that low carbing was going to kill you or make you sicker (and you trusted your doctor's assesment on that), what options do you have left?