The first and business class sections on some A346s are so heavy that they are pushing the jet’s nose down during flight, which can play havoc with the aerodynamics and potentially endanger passengers and crew.
If an aircraft has a forward C of G, the tendency will be for the nose to drop. This must be counteracted by the tailplane which generates downward force which subtracts from the total lift, requiring the wing to supply more lift to compensate.
This requires a higher angle of attack and therefore generates more drag which has to be overcome by engine power, requiring more fuel.
A rearward C of G requires up force from the tailplane which adds to the total lift, reducing what the wings need to produce and lowering fuel consumption.
As long as the loading is carried out within the certified limits no one is in any danger. A nose down pitching tendency is preferable to a nose up one which lowers airspeed and can lead to a stall.