If it is a card machine, shoot with the telephoto end of the camera, not too close. If you take a full-length photo, the camera should be as flat as possible with the model's chest and try to shoot horizontally, because the shorter the focal length of the card machine, the greater the shooting angle and the greater the deformation, the fatter people will be.
Tilt the model 45 degrees away from the camera. This photo will also look thin.
There are many ways to thin people. You should try your best to shoot, which is easy to master.