No.
During our grandmother's generation, women being fat before marriage was seen as not the norm. Women were prized for having 'dhaax yaar'.
Fatness and chubbiness is a new phenomenon found in the city. Our original culture is found in the meey and many poems talks about the maarin qalanjo with a long neck and small waist.
I've never heard of what you claimed here. Somalis used to say "waxaas oo xalus ah ayuu dhex dabaashaa" when they were describing chubby women ans their husband.
Fyi, chubby women can have dhex yar as well.