So many arguments here about how "the mean old airlines are squeezing us together!". The economic principle of the invisible hand is causing that, not an even James-Bond-villain. If 1000 people need to fly, and airplanes work at this weight and size, then we can fit X seats into the plane, where each seat is Y size. The problem is then when so much more of the population is becoming an outlier and "not fitting" into that seat.
You can have an argument on why people are fat now, and why it's getting worse, but that argument is not the purpose of sharing OP's article, I would reckon.
@Tennisace "If they are so large that they encroach into their neighbour's seat then they should buy 2 seats or buy a business class fare."
With this argument premise, I would say that I agree with your proposal.
Airline seat costs were designed based on price per space used, as the inside of an airplane is precious space.
Ergo, If you are larger than the X size of the seat, you are taking up more than your fair share.
Should we design larger seats? I really, really hope not. If 1 row of seats has 4 seats, each seat costs $100, then that row is worth $400. If we make bigger seats, then that $400 worth of space is now 2 seats of $200. Not only did we increase (drastically) the cost to fly, we have also (drastically) reduced the number of total seats available.
The Invisible Hand will take care of the rest and completely ruin air-travel as we know it.