Fat-craving gene discovered after scientists hold all-you-can-eat buffet

Scientists have found a reason why some people love a fat-rich chicken korma but are not so fond of a sickly sweet Eton mess in a discovery that could help treat obesity.

Most people find food that is rich in fat and sugar particularly appealing.

For centuries of human evolution, famine was a real danger so being able to stock up on calories could be the difference between life and death.

But the researchers found one group of people, who have a particular gene variant, like fat more, but sugar less than average, they reported in the journal Nature Communications.

It is one of only a handful of instances where a direct association between taste and the nutrient content of food has been demonstrated.

There also could be other genetic reasons why some people are more likely put on weight and it is hoped understanding the mechanisms involved could help lead to better treatments.

The researchers believe the preference for fat over sugar may be an evolutionary strategy that developed in some people.

Professor Sadaf Farooqi, of Cambridge University, who led the study, said: “When there is not much food around, we need energy that can be stored and accessed when needed.

“Fat delivers twice as many calories per gram as carbohydrates or protein and can be readily stored in our bodies.

“As such, having a pathway that tells you to eat more fat at the expense of sugar, which we can only store to a limited extent in the body, would be a very useful way of defending against starvation.”

The researchers tested three groups: people who were lean, obese or had the genetic variant, which affects a receptor in the brain known as MC4R.

The subjects were then given a taste of two different types of dishes – chicken korma and Eton mess – cooked in different ways but made to look the same.

The chicken korma had three levels of fat content, the Eton mess, which is made from strawberries, whipped cream and broken meringue, had three different levels of sugar.

Volunteers were then told they could eat as much of the food as they liked.

Although all three groups said they liked the three different kinds of korma about the same, the MC4R gene variant group ate 95 per cent more of the high-fat version than lean people and 65 per cent more than obese people.

While the lean and obese groups liked the high-sugar version of Eton mess significantly more than low-sugar versions, the opposite was true for the gene variant group.

The MC4R group liked the sweetest Eton mess about half as much as people without the gene and also ate about half the amount eaten by the others.

Professor Farooqi said: “Our work shows that even if you tightly control the appearance and taste of food, our brains can detect the nutrient content.

“Most of the time we eat foods that are both high in fat and high in sugar.

“By carefully testing these nutrients separately in this study, and by testing a relatively rare group of people with the defective MC4R gene, we were able to show that specific brain pathways can modulate food preference."

About one per cent of obese people have the MC4R gene variant, which may be part of the reason why they are putting on weight.