In an hour, especially if you can get in an hour 5 days/wk of weights/stretching/cardio, combined with a good diet should keep you in shape and the weight off.
Agreed. But an hour is a lot to ask most people before they start to realize some benefits. That's why I recommend the diet first and then short workouts. If those work for them, the desire to exercise will cause them to step it up themselves and do more activity because they have learned to enjoy it.