Standing up "tall" with the arms up is one of the classic fat-fuck poses because it stretches their rolls/fupa up and makes them seem less prominent. It can minimize a slightly portly 72" waist to a svelte 60" waist. Same reason the hogs who still have an iota of shame lay on their backs in their vomit inducing "sexy" dating profile pics. I am sorry I had to type those horrible words into the Internet, but much like the Fedex arrow, once you see it, you can't unsee it.