Sweet like chocolate?

Martha Gill's Irrational Animals column.

Easter turkey: low-calorie chocolate, Getty images.

For many Christians, the festival of Easter – hijacked, reduced, reconstituted – has become a bit of a sham. For God’s sake don’t let anyone do this to your Easter egg.

The government is worried about obesity. The solution, it feels, is to take all the foods that make us fat, then remove some calories. So now there’s a calorie cap: each Mars bar, for example, will have only 250 calories and in a couple of years calories in “a vast number of products” will be reduced by about a third.

A bleak prospect. For one thing, I can’t help but worry that this drive will spark a violent escalation in the kind of advert in which a thin woman fulsomely eats a chocolate bar at you. According to the writing on the screen, the bar contains barely enough energy to keep a canary alive – yet the eater is utterly blissful. “I can’t believe this bar won’t make me fat,” she says. “It makes me feel so good!” She’s lying. It doesn’t.

For companies that make fatty foods, the race is on to remove calories without tampering with taste. But health-conscious “chocolate scientists” have been trying to do this for years. In 2009, Swiss chocolatiers came up with a product that had 90 per cent fewer calories. It was given the Wonka-like nickname “wunder bar” but didn’t catch on. And in 2010, scientists at Birmingham University created a bar, mostly out of water, which they said tasted “exactly like” ordinary chocolate. The scientists were telling the truth. Yet everyone still prefers ordinary chocolate.

The golden ticket seems to be a substance that tastes and smells and feels exactly like chocolate but has far fewer calories. But the body is not so easily tricked. It turns out that the most pleasurable thing about a chocolate bar isn’t the taste – it’s the calories. The brain picks these up even if the tongue doesn’t. Can’t believe it’s not butter? Your brain can.

Scientists at Duke University in North Carolina demonstrated this using mutant mice. The mice were missing a TRPM5 channel, the receptor that detects sweetness. Place a dish of sugared water and a dish of normal water in front of these mice and they won’t be able to tell the difference – not at first, anyway. But the scientists then left the mice with the two dishes for several hours. Returning, they found the sugar water almost gone and the plain water barely touched. Even though the mice couldn’t taste the sugar, they had worked out they preferred it.

Pleasure principle

How could this be? The researchers looked at levels of dopamine, the reward chemical, in the mice’s brains. Sure enough, after the mice consumed the sugar water, there was a huge spike in pleasure.

Their reward systems weren’t responding to the sweetness in the sugar; they were responding to the calories. That’s why even the best fake chocolate in the world won’t work.

So this Easter, don’t try to trick your brain with health food. It will sniff you out. This ancient, calorie-demanding organ can’t be tricked by a few government initiatives and a little extra sweetener. It’ll simply make you eat more.

Or, to quote Jeff Goldblum in Jurassic Park: “Uh –uh – life – uh – uh – uh – finds a way.”