It depends on whether you consider intensity or duration to determine how "easy" a workout is. Sure, 2.5 hours is a lot of time to invest, but walking at 2.5 MpH hardly seems strenuous enough to qualify as exercise.

A 160 pound person could burn 500 calories in ~40 minutes jogging at a 10 minute per mile pace, and could easily offset a Big Mac in a single day's exercise (not saying that the person should use this to justify eating a Big Mac).