The math is a little bit closer, because even with fat pax the 777 has room in the belly for cargo.

With 91000# of self-loading cargo you can still cram about 50,000# in the belly. (I'm WAG-ging it here but I'm sure a 777 guy from AA, CAL, UAL or somewhere will tweak my numbers). You end up with about 87,000# more in the cargo version.

In a different job in a different time (ie before 9/11) I had a fleet manager at AA tell me that the AA 777 JFK-LHR flight would make $$ with NO pax on board - they were all gravy.

As another example of 777 fuel numbers, the typical DFW-MIA 777 (AA of course) dispatches with about 10% of the fuel tank capacity.

Bottom line - the airplane is extremely flexible. You can load it up with cargo and 10% in the tanks, or fill up the tanks and fly it for 16 hours.