I had a LOT of excess skin on my stomach after losing 50 pounds. I think I carried about 45 of those pounds on my stomach. I also had 2 enormous pregnancies which tore the underlying layers of my skin as well as my muscles and the central vertical ab ligament. My skin was shot by the time I was 28, it sure wasn't going to shrink when I was 46. I had a tummy tuck when I was 49. I took 2 weeks off work (should have been 3- I'm a personal trainer). I was doing light cardio by 2 weeks (walking) and lifting light by 3 weeks. Lifting back to normal by 6 weeks.
The rest of my skin looks like a normal 50 plus year old woman- not great, but it's not bad. Lifting heavy and eating right has made a big difference.
You actually start to lose some muscle after about 2-3 weeks, but you can rebuild much quicker than building in the first place
HTH,
Mel