I don´t think Scientology enables its followers to have lots of energy.
As far as I know, Cruise has been extremely driven since his troubled childhood, feeling he has to be better and work harder than anybody else in order to be loved and accepted.
When he became famous and one of the biggest movie stars in the world, he, of course, could afford all the help one can get to stay extremely fit.
Apart from that, his work ethic seems to be absolutely brilliant.
His beliefs have nothing to do with that, and reducing him to be a victim of a cult is what´s not fair here.