I removed wheat from my diet and it seems to be helping. I also stopped doing all heavy weighted ab exercises. I notice the difference and will start doing vacuums as I really want to shrink my waist.
I agree. Any movements that load the lower back like that can contribute to things. Although it's not quite black and white and people could deadlift twice weekly for years and keep a tight waist. I think pushing the poundages (over your limit being key) on certain movements over time combined with copious amounts of food can blow out the waist. Then of course you have other factors that contribute to things. I have done it myself and it's very hard to get back from it.