Born to hate broccoli: World-leading obesity expert on why your genes might be sabotaging your diet

A large proportion of food tastes are acquired.

Take the different types of starchy carbohydrates, which make up more than 50% of calories consumed throughout the world. My wife, who is of white Northern European ancestry, loves it in the form of bread. I am of Chinese ancestry, and can take or leave bread. Rice and noodles however, I can easily eat every single day.

Thus, the love of carbs is largely universal, but the ‘tastes’ for its different forms are culturally embedded from an early age. However, a lot of what and how we eat isn’t acquired. It’s built into our genes.

The top line from our expert

'Next time a dinner companion expresses a like or dislike for a specific food, it could be for cultural reasons, but it could indeed also have a genetic basis.

'Genes play a key role in some food intolerances. However, in my lab, we study the genetics of body weight, which we now know to be powerfully influenced by how our brain controls our feeding behaviour.

'Genes can influence your body to underestimate how much fat you’re carrying, so it makes you eat more as it believes you need more to survive. They can also make you crave sugar less or shy away from veg from the cabbage family.

'So next time someone you’re eating with passes on a certain food, cut them some slack. It could be their genes.'

Professor Giles Yeo MBE, professor at the University of Cambridge and honorary president of the British Dietetic Association. Read his expert insight on The one truth weight loss diets, injections and pills share when it comes to keeping off the pounds.

 

What gene gives you a food intolerance

There are well-known genes linked to food intolerances across different ethnicities. 

For example, I’m able to enjoy a beer or a glass of wine. However, I have a far lower tolerance than many of my white friends. 

This is because of a genetic variant of my Alcohol Dehydrogenase 1C (ADH1C) gene. We all carry two copies of the gene. However, I carry one copy of a variation which results in different alcohol metabolising speeds.

Many white people don’t have this variation, which is why they’re able to handle alcohol far better. However, my dad carries two copies of this genetic variant, which means he can’t cope with alcohol at all and can barely handle the bubbles coming off a glass of champagne (true story).  

Like many Chinese people, I am also lactose intolerant, because I don’t have the mutation in the Lactase (LCT) gene that many white people, for example, carry.

Makes you eat more fat

What is less well known is that there are actually genes that influence the ‘taste’ for certain types of food.

One of the key genes that plays a role in the control of food intake is the melanocortin 4 receptor (MC4R). This forms part of the circuit in our brain that senses how much fat we are carrying.

My research has discovered that around 0.3% of the UK population, potentially up to 200,000 people in the country, carry mutations in the MC4R, making them, at 18 years of age, on average 18kg heavier than someone without an MC4R mutation. 

Of that 18kg, 15kg is fat. Why? Because people with mutations in MC4R have brains that are less sensitive to the amount of fat in the body. Their brains think they are carrying less fat than they actually are. As a result, they eat more, and end up heavier.

However, the MC4R doesn’t only influence how much we eat, but also what we eat. 

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Can't resist high-fat choices

A colleague of mine here in Cambridge, Professor Sadaf Farooqi, devised two different experiments to try to understand the role that MC4R plays in influencing food choice. 

She tested lean individuals, and individuals with obesity with and without MC4R mutations. 

In the first experiment, she gave participants an all-you-can-eat buffet with three options of chicken korma (a mild, sweet, almond-based curry). 

The three curries were the same, in look, smell and taste, but differed in fat content, which was manipulated to provide a ‘Goldilock’s selection’ of 20% (low), 40% (medium) and 60% (high) of the calories from fat. 

What happened was those carrying a mutation in MC4R ate almost twice the amount of high-fat curry than the lean individuals ate, and 65% more than individuals with non-MC4R obesity.

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Curbs your taste for sugar

In the second experiment, the same three groups were given Eton mess, which is, in effect, what happens when someone drops a Pavlova of strawberries, whipped cream and meringue on the floor, and scoops it back in a bowl. 

Again, there were three options from which to choose, this time differing in the amount of sugar present in the meringue and cream, providing 8% (low), 26% (medium) and 54% (high) of calorific content. 

Paradoxically, in contrast to the fat choice experiment, individuals with a mutation in MC4R liked the high sugar dessert less than their lean and obese counterparts and in fact, ate significantly less of all three desserts compared to the other two groups. 

It turns out that people with a defective MC4R preferred higher-fat food, but had a decreased preference for sugary foods.

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Makes you hate green veg

How about the taste or distaste for specific types of food? Brussel sprouts for instance?

I once did a talk at the Royal Institution in London about the genetics of feeding behaviour, and performed a demonstration with 12 people from the audience. 

Everyone got a little blank bit of paper, and were told to put it on their tongue (I did it to, to reassure that I wasn’t trying to poison anyone). 

Half of the volunteers (including me) encountered an acutely bitter taste, while the other half tasted nothing, and were looking around, puzzled by the difference in reaction. What was going on?

Well, all the pieces of paper were infused with a little drop of phenylthiocarbamide. That’s the chemical responsible for the bitter taste found in brassica, plants in the cabbage and mustard family, which include Brussel sprouts. 

However, only around 50% of people, known as ‘supertasters’, carry a variation of the gene TAS2R38, that allows them to detect the bitterness. The ability to taste this bitterness doesn’t automatically mean you hate sprouts, but it certainly influences the taste sensation you get from eating them and other related vegetables.

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Why you might detest coriander

Then there is the marmite reaction of different people to the herb coriander – or cilantro, depending on where in the world you hail from. 

Many people, including me, consider it tasty. However, some, most famously the chef Julia Child, find it disgusting. Julia said she’d throw it on the floor if she found it in food. 

This dislike may, of course, simply reflect preference. However, for those coriander-phobes among you, for whom the herb has a strong soapy taste, it is indeed genetic. 

Some people have a genetic variation in the olfactory-receptor gene OR6A2, allowing them to strongly perceive the aldehydes in coriander leaves, which are the source of the soapy flavour. 

Interestingly, the prevalence of this genetic variation varies geographically. Regions where coriander is more popular, such as Central America and India, record fewer people carrying this ‘soapy’ variation.