Private Custard said:
If an A380 flying to Singapore has a full allocation of 471 passengers, weighing 80kg each, thats 37.6 metric tonnes.
Now pretend all the passengers are fat. We're talking serious increases in fuel useage.
Say that the fat you're talking about is an extra 30 kg, means an extra 14,130 kg, so an extra 14.13 metric tonnes.
The empty weight of an A380 is about 276 (252 with different model) metric tonnes, add to that the base weight of the healthy crowd - 37.6 metric tonnes, total there is 313.6 metric tonnes.
At that point the extra 30kg per person would mean an extra roughly 4.5% in weight.
But, that's not accounting for the base weight of fuel which would be required to transport the base passenger weight.
Pretty sure if you found that amount, then the increase in total weight by the 'fat' passengers would be likely about 2% increase in weight.
Would anyone here actually know the amount of fuel an A380 would actually requires for a base passenger weight, and is able to quantify just how much fuel would be required for a 2-4% increase in total weight?