The gene, called FTO, was found by studying the genome of 39,000 white people in the United Kingdom, Finland and Italy who gave blood samples, the team said in Thursday's online issue of the journal Science.

People who had two altered copies of the gene were about three kilograms heavier on average, and had a 70 per cent higher risk of obesity than people with no copies of the gene. Those with one copy had a lesser but still elevated risk of having a higher fat mass.

The researchers behind this study believe that people who carry a more active form of the GAD2 gene build up a larger than normal quantity of GABA in the hypothalamus, and suggest that this over accumulation of GABA drives the stimulus to eat further than normal, and is thus a basis for explaining why obese people overeat.