Fat-craving gene uncovered with all-you-can-eat korma study

I won’t lie. If I saw a sign saying “subjects required to test free all-you-can-eat chicken korma buffet”, I would already be filling in a holiday request form. That says a number of things about me, none of them particularly flattering, but the study revealed something interesting about the actual participants too. Namely that those with a mutation in their MC4R gene are genetically drawn to high-fat food, even when it tastes identical to a low-calorie variety.

Here’s how the experiment went down. Scientists from the University of Cambridge invited 54 people to an all-you-can-eat chicken korma buffet knowing that 14 of the participants carried the defective gene. The remaining 40 guests were either lean or obese. Three chicken korma varieties were made available, all designed to taste the same, but with different fat content (20%, 40% and 60% respectively). Participants were encouraged to sample each dish before getting properly stuck in, without being told which was which.

Here is where it gets interesting: while everyone ate similar quantities of food, the researchers found that the participants with the mutated MC4R gene consumed 95% more of the high-fat korma than skinny diners, and 65% more than obese eaters.

Tables were turned when it came to dessert, however. In a second part of the study, participants were given three kinds of Eton mess, with sugar levels ranging from 8% to 54%. This time, there was no difference in each one’s fat content. Not only did those with the defective MC4R gene eat less of the high-sugar dessert, they actually consumed considerably less of all three desserts than other participants.

So, what does this tell us? That our brains can detect nutritional content, even when flavour is “tightly controlled”. As Professor Sadaf Farooqi, from the Wellcome Trust-MRC Institute of Metabolic Science at the University of Cambridge, explained: “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.”

And why would we do that? Evolutionarily, Professor Farooqi believes it’s simply a method to get more nutritional bang for your buck. “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.”

It’s worth noting that the MC4R gene mutation is pretty rare, estimated to affect around 1% of obese people. The really interesting take-home from this is that no matter how delicious that low-fat food tastes, subconsciously, our brains know better.

Image: Cyclonebill used under Creative Commons