If you've grown, the simplest thing to do for starters is to move the apron buckle(s) and the underapron strap over. If the underapron shows much, however (and that will depend on where the kiltmaker put the buckles and straps to begin with), you'll need to have the kilt let out, as Matt says. 2" can be accommodated easily, and the kilt will look essentially the same after the alteration.

If you're losing weight, I'd definitely move the buckles and strap rather than doing any major alteration until you're sure where your weight will settle. It's something you can do yourself, and it really isn't noticeable. One of our pipers lost 70 pounds, and I've moved the buckles and straps on her kilt over 5" on each side. Yes, the apron goes farther around the kilt than it should, and the center back stripe isn't in the center back any more, but you really have to look to notice it.

Just remember that you move only the apron buckles. Moving the buckle near the buttonhole doesn't do anything. Instead of moving that buckle, you move the underapron strap closer to the edge if you need more room or toward the center if you want the kilt tighter.

Let me know if you need details!

Barb