Any activity helps. The key is to stay active all day. Why sit when you can stand, why stand when you can walk, and why walk when you can run
I do crunches and walk in place during commercials. I park far away. I take the stairs. I only do about 20-30 minutes of formal exercise 2-3 x week on the Bowflex. (Well, I was before having PS). Unless you're training for an event, don't make it a goal to get in 1-2 hours a day of exercise.