Far away in the Pacific island of Samoa a fascinating experiment in the nudge theory of behaviour change is unfolding. The national airline, Samoa Air, has decided to charge passengers by the kilo to fly.

Not per kilo of luggage, but per kilo of the combined weight of the passengers and their luggage. The airline claims that this is the fairest way to fly.

The island has long grappled with one of the highest obesity rates in the world, with 92% of over 15s reported as overweight, so it is easy to see the problem the airline is trying to tackle.

The economics of the decision add up: the running costs of planes are dictated by weight. Samoa Air maintains that the rest of the industry will look closely at what they’re doing. That may be true, perhaps no more so than among distinguished Irish-based airlines.

What’s intriguing about this though are the implications of the new policy.

Putting fairness for tall people aside (who would pay more than short people here) it sends a very clear signal about expected “normal” behaviour.

If it helps promote healthy eating, then what else could we anticipate?

As we have seen with smoking cessation here, communications have a role in normalising good behaviour (and demonising the “undesirable”), but it is debatable whether hitting people in the pocket really changes how people behave over anything.

The implications of this are pretty clear, not only for the obesity debate, but also for the discussion around minimum pricing of alcohol. While it may be tempting to penalise financially “undesirable” behaviour, the jury is out as to whether it really works.