Important new paper: Why do some people prefer fatty foods?
Most people find high fat, high sugar foods particularly appetising. This can lead to eating more calories than we need and can contribute to weight gain. But what influences food choice? The taste, appearance, smell and texture of food are all important, but do genes play an important role?
In a study just published in the journal Nature Communications, we looked at the MC4R gene. Previous studies have shown that disruption of a particular pathway in the brain involving the melanocortin-4 receptor (MC4R) can lead to mice eating a lot more fat. Unusually, these mice eat a lot less sugar. However, the relevance of these findings to people has been unclear until now.
What did we do? We gave people an all-you-can-eat buffet of chicken korma - a popular type of curry - with three options: low, medium or high fat. We had carefully prepared the meals so they looked and tasted the same. We then tested normal weight people, overweight people and people who were overweight because they have a faulty gene called MC4R.
After taking a small taster of each meal, people were asked to eat freely from the three kormas. They could not tell the difference between the foods and couldn't tell that the fat content was different. We found that, although there was no overall difference in the amount of food eaten between the groups, people with a defective MC4R gene ate almost twice as much high fat korma as normal weight people.
In a second study, people were given low/medium/high sugar versions of Eton mess, a dessert that includes a mixture of strawberries, whipped cream and broken meringue. Normal weight and obese people said they liked the high sugar Eton mess more than the other two desserts, as you might expect. However, people with a faulty MC4R gene liked the high sugar dessert less than their normal weight and obese counterparts and in fact, ate significantly less of all three desserts compared to the other two groups.
One in 100 obese people have a defect in the MC4R gene which makes them more likely to put on weight. For these individuals, the fact that the MC4R pathway is not working may lead to them preferring high fat food without realising it and therefore contribute to their weight problem.
Professor Farooqi, who led the research team, says: "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."
This is one of the first studies to show a direct link between food preference and a specific gene.