Gastric bypass has given us many thousands of men and women who are now heathier and happier at their new lower body weight. But it's also given us thousands of people who have loose skin nearly everywhere on their bodies. The skin quality is damaged by the stretching of the skin, not the loss of the weight. The damage is done even before any weight loss. Compression garments help control SWELLING after surgery; they wil not help replace collagen and elastin in damaged skin.
There is no way to prevent loose skin after massive weight loss. If you're going to have it, you're going to have it. Very few people are blessed to NOT have loose skin after massive weight loss. Enjoy the other fantastic changes that come along with the weight loss; focus on your new habits, and don't stress about your skin in the beginning, as it's out of your control. Best wishes!