The author dilutes and weakens his argument by bringing up obesity. Whether a 80kg person is 40% fat or 10% fat doesn't matter; the central point is that a person who weighs more, consumes more, and thus ought to pay more. I wish he stuck more to that point instead of running off on the tangent about health and the environment.

Friends with whom I discuss this proposal often say that many obese people cannot help being overweight – they just have a different metabolism from the rest of us.

To expand on the author's take on why this argument is weak, take for example nearsighted people. Nearsightedness is partly hereditary; similar to obesity, it can be exacerbated by certain choices, but some people are just bound to be nearsighted. Nearsightedness means paying for glasses (at least the deductible) and often paying a huge premium for sunglasses. Simply put: life isn't fair, and people are already paying different expenses just because of conditions they were born with.

Tony Webber, a former chief economist for the Australian airline Qantas, has pointed out that, since 2000, the average weight of adult passengers on its planes has increased by two kilos. For a large, modern aircraft like the Airbus A380, that means that an extra $472 of fuel has to be burned on a flight from Sydney to London.

That said, is such an initiative necessary, cost-saving, or beneficial to the customer? An Airbus A380 holds about 600 passengers. That comes out to about $0.75 per passenger per 2 kilograms.

A pretty average American man weights about 85kg. A very light American man (bottom 5%) weighs about 65kg. A very heavy American man (top 5%) weighs about 115kg. (Pulling data from this chart). This means that the lightest 5% of men would pay about $7.50 less for a Sydney-London flight than average, and the heaviest 5% of men would pay about $11.75 more. On a shorter, domestic flight like Chicago-NYC, those figures work out to maybe a $5 difference in ticket price between a 65kg man and a 115kg man - and that's not even counting in the extra costs associated with spending time on weighing passengers!

So with that taken into account, I don't think that this is the best idea. Maybe extremely heavy people who are literally spilling over into the seat next to them should be forced to purchase two seats or upgrade to a roomier first class seat, because it's not fair for the poor guy sitting next to him. But the weight-to-fuel-price argument seems to not be strong enough. Maybe it'll be worth revisiting if fuel prices climb significantly.