does doggy make your butt bigger

so I saw this picture, and I was like well my boyfriend needs to figure out what he's doing wrong because I've been happy for about nine months now. and my friend saide "you get why, right?" and I thought it was because she got comfortable and was eating more so I say… I don't know, he feeds her? and she was like "back shots make your butt bigger, I wouldn't know though because I've never done it but that's what I've heard." and now I'm like "is that all it takes?" we've been having sex for a while now, not usually in that position, but my butt is still tiny. I told her that I am very doubtful that's true because I don't actually know how that would even work, theres barely a correlation and she looks like she just gained weight in general. but I've actually heard this a couple times