If I recall, the phrase you are referring to was meant to describe people on T.V.. Apparently when you are on T.V. You appear much "larger". I do not think it refers to still photography or video.
This is not a troll question... what camera are they referring to when they say "the camera adds ten pounds"? Is it only video camera or is it still pictures as well?
Many years ago there was a female newsreader, Angela Rippon. We all assumed she was a little overweight, because she appeared to be so on the small screen. Then she did a guest spot as a dancer on the Morecombe and Wise show.
http://www.bbc.co.uk/programmes/p00bpkwp
This site will give you some insight into what's going on:
https://petapixel.com/2012/07/17/why-the-camera-adds-10-pounds-seeing-ourselves-in-pictures/
This may not be a camera but probably a Hehnway . . . .
