They’re ‘intrinsic exercisers’ - that is, they exercise because that want to, not because they have to.  The key?  Unstructured exercise, or as I refer to it, exercise you’re not even aware of.

In The Intrinsic Exerciser: Discovering the Joy of Exercise, author Jay Kimiecik cites several studies that three 10-minute ‘exercise sessions’ are the same as one 30-minute session.  What this means is, if you just motivate yourself to move a bit more during the day, you’d be getting as much exercise as if you went to the gym every week:

A 10-minute walk to to work or transit in the morning, a 10-minute walk to and from lunch, a 10-minute walk home, and a 10-minute walk to visit a friend or run an errand.  Suddenly, you’re in great shape and probably thinking to yourself, “Hmm, I must have great metabolism.“