It's a concept referred to as "NEAT", or non-exercise activity thermogenesis. It's essentially saying that your physical activity throughout the day, just moving around doing what you do all day from chores to climbing stairs to walking around the hallways at work, can burn as many or more calories as a workout at the gym. 

I don't know, folks. Sounds like it was conceived by someone who just didn't want to hit the gym. 

But you can decide for yourself.