You can quickly see the difference in the two photos. Both photos were taken seconds apart. Notice how much thinner I look in the second one. A good model will stretch herself/himself as much as possible and also suck in the tummy area. Also if the one taking the photo puts the camera at a slightly different angle from the subject the results are fabulous. You can clearly see that the second photo is the most flattering.
You might want to try this at home and I think you will be happy with the results. Hope this lesson was helpful to you.