The old standard weight of 170lb (77kg) dates back to a North American population study of US male military personnel. The date of the report eludes my doddery memory but somewheres back in the war years or shortly after.
What amazes me is that the weight was reasonable for so long. I can recall on the F27 in the mid-70s often weighing the pax when fuel was supercritical .. with the pax numbers around the 30-40 mark, 170lb was pretty well spot on.
Acknowledging the increasing Australian rate of obesity, CASA Airworthiness ran a very detailed study - by John K - around 30 years ago. The study was based on Australian National data and was a rational representation of the then Australian population.
After a few years of frustration for John, his report eventually was promulgated to the Industry and its main elements still form the basis for the present
CAAP 235-1.
I would be surprised if CASA went along with the use of 77kg these days unless an operator could put up a very strong argument to undervalue the CAAP ?
If folks can find a copy of John's original report, which provides considerable detail of the statistical protocols (for non-statistician users) which are sensible to use, the process could be reworked for current population sample data.
Some of the Island populations (along with football teams, Sumo wrestlers, etc.) definitely warrant weight control calculations run on a basis different to the CAAP ....