Excellent response from TbombZ.
If waist is getting wider, than check the diet. Though the obliques, as a supporting muscle group, can become a little thicker with squatting/DL's. Not being a large muscle group by nature, it should not be that noticed. Actually the ancient Greek & Romans favored obliques as a sign of power. Well developed in all strongmen lifters these days.
With due respect respect to my PL'ing friends: Those extra wide PL'ers, with overblown belly's and wide waist, just carry too much fat. There are very fat men, exceptionally powerful, with usually red line high blood pressure. The lighter division lifters tend to be more in line with BB'ing development. Exceptions of course. Good Luck