How do I convince my severely obese brother to have Gastric Byp surgery?

Having gastric by p surgery won't change the outcome. Yes, he may lose the weight for now, but he will gain it back sooner or later if he doesn't lose the weight for the right reasons. It has to do with attitude, and trying to tell someone that they need to lose weight makes them rebel. He knows he needs to lose the weight, but right now nothing is motivating him to do it. More time than not, some people who have this surgery, gain it back plus add even more weight. Losing weight isn't the issue, his mental health is. Maybe he should seek counseling to find out why he wants to abuse his body. Other than that, nothing you or your parents say will make him change his mind. Stop the nagging and let him decide on his own. He may never do it, but it is his choice.