I wore one I got from Walmart, not really a waist trainer, but it helped suck in everything. I wore it a week after a gave birth, for a few weeks on and off and it seemed to help, although I don't have much to compare it too. it helped my belly not feel so jiggly until it tightened back up on its own.
im going to do a belly bandit wear it for 6-8 weeks after baby then switch to my girly cirves waist trainer i had before baby. it worked for me after the first baby :)