How to train elephants, drink less and lose weight

Rory Sutherland

Rory Sutherland explains why it is easier to change behaviour by using simple rules than by using rational argument.

"And Jesus went into the desert for forty days and forty nights, and there ate modestly of a low-calorie diet, with some special low-fat falafel, which he had found at a shop just off the Jericho bypass."

You don't get that in the Bible. In fact, biblical folk don't diet at all. They fast. Religious law, you'll notice, tends to be binary and prescriptive – it isn't generally quantitative at all. "Don't eat between dawn and dusk." "Don't eat pigs ever." "Don't eat meat on Fridays."

There may be a good reason for this. When was the last time you broke the speed limit? Unless you live in London – in which case it may have been simply impossible – I would be willing to bet it was the last time you drove a car. Yet when was the last time you ran a red light on purpose? Even at pedestrian crossings where there isn't a pedestrian in sight for miles, we mostly wait for the amber light to start flashing.