You can't do it in any knitted sort of way. This is why it's so important to check your gauge first. BUT, if the fabric isn't too thick, I would think you could sew new seams with a sewing machine... very well, probably two lines of stitches would suffice, cut off the excess fabric, and surge the edges to secure.
Pretty scary way to do it though, in my opinion. You could do like me and let it be a lesson on checking gauge. I have a super huge sweater too.