I'm not really understanding people thinking its a different proportioned model. All the proportions are pretty much the same in both images, the difference is in perspective. In the first, chest is to the side, hips are bent to face to the camera, and out to accentuate the hips, thus making them seem larger and the waste seem smaller. The second image (which is a better, less exaggerated pose), is far more casual, with both hip and chest facing the same direction.
Its literally just a pose change. Its for the better, but some people here are weird in their exaggerations, geez.