I'm 39, and though I trained in mma, bjj and kick boxing like 10 years ago I hadn't done much of anything since 2006. In March I decided I had gained too much weight and dieting wasn't going to cut it. A friend had been doing Krav Maga and I decided to give it try. After 4 months I was down 22lbs (190 to 168) and feel 100 times better. The first month was rough but now I feel bad when I don't go, another 10 lbs to my ideal weight when I was in great shape.
For those curious, Krav Maga is a self defense system from the Isreali military,pretty much a combo of kick boxing, bjj and wrestling with a focus on fitness and no rules ie hit the nuts and throat if you can. I can't speak for the system as a whole but the New Orleans school is legit with instructors who compete in mma and lots of law enforcement people. Personally, for me it's more about going cardio bag class and getting pushed for a straight hour of punching, kicking and whatever cruel exercises the instructor has decided on that day