Short waist width is an important part of an attractive feminine figure. The apparent size of the waist is generally limited by the bottom of the ribcage, with males having shorter and more broad lower ribs, making relative waist size a sexually dimorphic feature[1].
Corsetting
https://www.corsettraining.net/waist-corset-training-timescale/
https://www.corsettraining.net/waisttrainers/waist-training-before-and-after-corset-training/?amp=1
Waist Surgery
Sometimes known as ant-waist surgery. It involves either a removal or reconstruction of the lower 2 false ribs, creating the appearance of a more narrow waist after recovery.
https://pubmed.ncbi.nlm.nih.gov/36891563/
https://journals.lww.com/prsgo/fulltext/2021/07000/waist_narrowing_without_removal_of_ribs.9.aspx