Depends on how long you are resting. But you could do it within an hour.
But I wouldn't get too caught up in the "you should only be in the gym for an hour thing" as there's some myth to it all
I agree Whole Heartedly, I work for myself , a lot of hours. I dont have more then an hour a day. But when I go in I do it hard and lil rest. And As far as i can see , I am getting better results then most of the Gym rats that hang out 3 hours a day.
How long do those full body workouts last though? I've always been trained to believe you should be in the gym for only about an hour.
As said above, it depends on how much rest you take. It also depends on the number of exercises and sets performed. You can save time by focusing on compound movements - they work a lot of muscle groups at once.