Posted on by Ed Yong

On Friday, the media was abuzz with the discovery of a ‘gene for obesity’. Researchers funded by the Wellcome Trust found that people who carry a single copy of a variant of the FTO gene are 30% more likely to be obese than people with no copies.

But one in six Europeans carry two copies of this variant, and they are 70% more likely to be obese. On average, these dual carriers weighed three kilograms heavier than their peers.

The FTO gene itself is a mystery. Noone knows what it does or even which other genes it interacts with, and the Wellcome Trust team are now probably itching to find out.

But in this case, the reaction to the discovery was almost more interesting than the science itself. If internet talkbacks are any indication, people roughly fall into two groups.

To the first camp, the findings echo their own experiences of finding it difficult to maintain a healthy body weight. It points to something deeper and innate at work.

But the reactions from the other, slightly louder camp have been acrimonious to say the least. To them, the discovery of the FTO variant is yet another way for obese people to brush off the burden of responsibility from their shoulders.

After all, they say, obesity is just a matter of eating healthily and exercising regularly. To go beyond this is to over-complicate a simple lack of willpower. And where exactly was this gene in post-war Britain when obesity levels were much lower?

This attitude couldn’t be more wrong or more unhelpful, and many of these complaints misunderstand the nature of obesity-related genes.

It is clear that obesity has some genetic basis, but no researcher worth their salt would imagine that a single gene dictates whether a person becomes obese or not.

Obesity-related genes are likely to work through much more delicate ways. Some may affect how we metabolise food or lay down fat. But subtlest of all are genes that affect our very behaviour.

These inherited influences could make individuals more responsive to the smells or sights of food. They could make the brain less responsive to signals from the gut that say, “I’m full.” They could give people a strong innate preference for the chemicals that give fatty foods their taste, or equally put them off the chemicals (often bitter ones) within healthier choices.

In a society where food supplies are modest, say post-war Britain, variations in such genes across a population wouldn’t have much effect. But in the 21st century, things are very different.

With more junk food widely available at cheaper cost, and active lives replaced by office jobs, cars and the telly, it is notoriously easy to eat lots and do little. In this environment, small genetic differences that affect how people react to food or activity can have massive effects.

So where was the FTO variant in post-war Britain? Well, in all likelihood, it was around, but its effects have been masked until now. Genes and environment interact with each other to affect our lives – nature and nurture usually walk hand in hand.

Obese people are likely to carry around a host of genetic variants that alter their behaviour in ways that leave them very vulnerable in a world where obesity is just around the corner. Obesity then, is a complex disease with many underlying causes.

And because of this, throwing words like ‘self-discipline’ and ‘laziness’ about with cavalier abandon does nothing for the obesity debate or for obese people themselves.

After all, where are personality traits like ‘discipline’ housed, if not the brain? And what controls behaviour and the development of the brain if not genetic information?

Is the combination of genes and environment an excuse for obesity? Hardly. But it does go some way toward explaining it, which is more than an accusation of faulty willpower will do.

Scientists hope that the discovery of genetic variants that influence the risk of obesity may one day herald new treatments for obesity. But this is a distant dream. For the present, very little actually changes for obese and overweight people.

To overcome the effects of genes and environment, they must still make lifestyle choices. The old maxim of “eat well, be active” still applies. The real benefit to FTO’s discovery would be a change in the attitudes of everyone else, from damning to supportive and from accusatory to understanding.

More on obesity:

A mismatch between nutrition before and after birth can lead to poor health

Human gut bacteria linked to obesity

Reference: Frayling, Timpson, Weedon, Zeggini et al. 2007. A common variant in the FTO gene is associated with body mass index and predisposes to childhood and adult obesity. Science 10.1126/science.1141634.

Image: Photographs by Boochan and Clarita

Technorati Tags: obesity, fat, genes, obesity+gene, fat+gene, science, FTO

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Filed under: Genetics, Health & Medicine, Obesity, Psychology, Science & society |