So this is a spin-off of another post because I've seen the topic here many, many times: back fat.
Back fat isn't usually fat though, it's frequently migrated breast tissue from wearing an ill-fitting bra. Some 80% or more of women wear the wrong sized bra. I'll include a link in the first comment that goes into more detail, for ease of copy/pasting, but for me, it was literally life-changing!
Stores that measure incorrectly, like VS and JCPenney, all claimed I was a 40DDD. I dealt with quad boob for years thinking they were the bra people, they knew what they were talking about. Ha, no. When I measured by this blog's instructions, I was a US 36O/P! That's a HUGE difference, and I feel SO much better, no back pain, clothes fit better, etc.
So if you're trying to get rid of back fat, you might check out your bra and see if it might be the culprit, because you can't work migrated breast tissue off like you can fat.
Hopefully this helps others!!