I was sitting off to the side of the stage last week in Anaheim and was able to see Charlie do his little jig before the show started.
During the fan video, he and the rest of the band were behind the visible part of the stage and he started tapping his feet and doing his little dance.
A sense of timing is more of a prerequisite for drummers and musicians in general than is fitness.
Ginger Baker can still play the drums and does so with a sizeable paunch as well as degenerative osteoporosis.
Besides, Charlie is slim more out of vanity than fitness--just look at the way he dresses.
The sort of drumming exertion the article discusses describes mainly the hard rock/heavy metal/trash type of drumming more suited to drummers of a certain age.
Most important, Charlie as a drummer is more like a knuckleball pitcher in American baseball, the type of pitcher who doesn't throw hard and relies more on finesse--those types of players last longer than average as a result. By his own admission, Charlie doesn't even hit the drums that hard.
Be fat. Be happy. Play drums. Play fat.
This anti-fitness message brought to you by the following "big fat drum solo"....