Common gene variant affects risk of obesity

UK researchers have discovered that a common gene variant helps explain why some people are more prone to gaining excess weight than others. Adults and children with two copies of a particular version of the FTO gene are, on average, three kilograms heavier than people who do not have the variant. The team, lead by researchers at Peninsula Medical School in Exeter and Oxford University, first identified the variant during a search for genes that influence the risk of Type 2 diabetes. Their findings, published online by the journal Science, are based on data from around 39,000 people.

While the 'obesity epidemic' of recent years is probably due to changes in diet and lifestyle, previous evidence from twin studies strongly suggested that genes also play a role in weight gain. A US study published last year claimed that variations in the INSIG2 gene contribute to the likelihood of obesity, but their findings have not been replicated in all populations. In contrast, there's 'very strong evidence' that the FTO gene affects body weight, according to geneticist David Altshuler.

Half of all white Europeans carry one copy of the FTO variant, which confers a 30 per cent increased risk of obesity. Around 16 per cent carry two copies, which together carry a 70 per cent increased risk. The team don't yet know what the normal role of the FTO gene is in the body, but they hope that further studies will help shed light on the biological basis of obesity - the variant could make people burn calories less efficiently, or it could influence appetite, for example. Team leader Mark McCarthy believes the gene could be a useful target for new drugs to tackle obesity, although he stresses that the recent rise in the incidence of the condition are down to diet. 'The gene pool hasn't changed in 20 or 30 years', he told New Scientist, adding 'I don't think you can say that [the FTO gene variant] has caused the obesity problem'.