Everybody knows about backs. No one dies of large breasts. But breasts can be a large-sized pain, the Marilyn Monroe myth notwithstanding. Unlike tummies, they aren't supported by muscles. But judging by my experience, the weight of two soup cans sitting on the chest of a small woman for decades is enough to pull the shoulders forward.
Bigger women can carry bigger breasts.
Support bras can distribute the weight across the shoulders and back. But bra straps dig into the flesh at the shoulder, making permanent gullies. They don't do so painlessly. At age 58, a person of medium height with small bones and narrow-hips, I was having lower back pain. I once had the frightening experience of waking up unable to get out of bed.