Taking in Some Jeans

What you need to do is at the left and right back, make V-shaped tucks in the waistband. If you have a sewing machine that can handle a few layers of denim, you should be fine.

Celebrate your weight loss with NEW jeans!

In addition to what OneAndDone said: in the center of the back , there is a stitch (for jeans, it's usually a double stitch which is tougher). You can undo it, cut some material out and sew it back up. At the waistband itself, cut exactly at the center of the back, remove as much material as you need and sew it back up, hiding the seam behind the belt loop. This is what most alterations place do to slacks. It's not easy to do for jeans because of the thick denim material, so I wouldn't mess with it unless it's your favorite pair and you don't want to toss it.
Hey, I just googled "How to alter jeans in the waist". Here it is:
http://playgroupsarenoplaceforchildren.com/2009/07/15/sho...

Take some strong elastic, anchor it down on one side of the waist band, perhaps zigzag it. Then stretch it across to the other side a bit and anchor it down. Take pins and stretch it out then pin it in the center back. Then center that section and so forth. Until you have pins every couple of inches at most, I usually do about 1 inch apart. Use a heavy needle in the machine, denim is thick on the seams and hard to poke through.

Sew from top of the elastic to the bottom, I sew about 1/2 inch to 3/4 inch apart. This allows the elastic to stretch between the little seams that go up and down and it also strengthens the elastic and gives it elasticity without sewing it down all the way.

I would have it professionally done even though you know how to sew and have a machine. A lot of dry cleaners also have reasonably priced tailors. There's one in Eagan in the Cedervale area I've been very happy with. PM if you want the name. I can't remember it right now. Congrats on your weight loss.