There are only two guys capable of soloing a 4U install where I work, myself and this other dude. We're also the only people in the building with weights that have a 1 in the first digit...what a coincidence huh? With that said, soloing a 4U server is an "emergency" maneuver. Almost all of them are over 100lbs and nearly 3 feet long with a variable center of gravity depending on config making it almost impossible to properly lift. Fat guy legs won't save you here...you need a strong back and core.  So yes, not being fat can be good for uptime.