There is a "standard weight" of around 90kg per passenger used for flight planning purposes. However, believe me that the pilot or the dispatcher would almost certainly have had a look at those involved (thought probably not saying so) to see such a gross anomaly from the standard weight was not happening.

An accident in the USA some years ago was initially (though incorrectly) believed to be due to a large load of sportsmen in the aircraft which could have upset the balance, and procedures were redefined after that to ensure the standard weights did not in themselves lead to imbalances.

The substantial change in aircraft gross weight during the flight as the fuel is consumed is not significant as the fuel tankage is designed so it lays equally forward and rearward of the nominal centre of gravity of the aircraft no matter how much or little fuel is on board.