I am in shape. I ran a 56 400m the other day. That's not competitive, but it's in shape. I average about 2.5 "workouts" per week, but it's not rare that I go a week without exercising at all. Nothing I do takes over 35 minutes, except for long bike rides, which I don't really do regularly.
Unless you're training for an endurance event, you do not need to spend a lot of time exercising to get into the top 20%. And if you ARE training for endurance I would recommend against it if your goal is health, because endurance athletes have health problems.