The gene in question (known as FTO)has two variants: low risk and high risk. 16% of the population have two copies of the high-risk variant, 50% have one high-risk and one low-risk, and 34% of people have two low-risk variants.
People who inherit one version of high risk variant are more likely to be obese. Those who inherit two copies of the high risk variant weigh an average pf 3kg (almost 7lbs) more than those with two copies of the low risk variant. They also have 15 per cent more body fat.
Family studies have indicated that obesity is influenced by genetics (and not just behaviour), while mutations have been found to cause rare obesity disorders such as Prader-Willi Syndrome. The findings, however, provide the first link between a common gene and a tendency towards obesity. If the biological function of FTO can be understood then it may be possible to design drugs that manipulate it to help people to control their weight.
The effect of FTO emerged from a key study of the genetic origins of disease funded by the Wellcome Trust known as the Case Control Consortium, in which 2,000 people with type 2 diabetes had their genomes compared to 3,000 healthy controls. Scientists from Oxford and the University of Exeter first found that certain versions of the FTO gene were more common among people with type 2 diabetes, but that the effect disappeared when the data were adjusted for obesity. This led them to wonder whether FTO really influenced obesity instead, and they followed up their theory in a further 37,000 people.
FTO will not be the only gene that influences obesity, and inheriting a particular variant will not necessarily make anyone fat. “This is not a gene for obesity, it is a gene that contributes to risk,” said Professor McCarthy of Oxford University. The research involved too many people to control for exercise and diet, so it is not yet known whether FTO affects how much people eat or how active they are. But it may explain how people with apparently similar lifestyles differ in propensity to put on weight.
Independent experts called the discovery highly significant. Susan Jebb, of the MRC Human Nutrition Unit, said: “This research provides clear evidence of a biological mechanism which makes some people more susceptible to gaining weight in a world where food is plentiful and sedentary lifestyles the norm.”
Finding a genetic element in obesity is obviously not the end of the matter and is not the “get out jail free” card for those of us who need to stretch our necks a little just to see our toes! There is obviously a lot of research to do yet and this research may provide drugs that help control our weight. However, we have an increasingly sedentary lifestyle and no amount of drugs will overcome that. At the end of the day sensible eating and exercise will continue to play the major role in controlling waistlines.... Now to practice what I have just preached!