I didn't watch the video yet but I remember a study that was done where two people were placed in separate rooms for 12 hours.  They each had a TV, radio, some reading material, snacks and furniture.
One of the people was about average build and the other was somewhat pudgy.

The average build person was moving a lot, either fidgeting or up walking around while the pudgy person plunked down and was immobile for almost the entire time.  It was concluded that some people are simply more active, even if it's drumming their fingers or bouncing the leg.