Scientists have discovered a gene that ups the risk of obesity, a breakthrough which they claim offers insight into why some people put on weight while others with similar lifestyles stay slim.
A British-led team has found that people who inherit two copies of the variant, which lies close to a gene called MC4R, weigh an average of 1.5 kg more than those without the genetic variation, the Nature Genetics journal reported.
According to the scientists, this variation combines with a gene known to influence obesity, called FTO.
People who carry the most damaging versions of both the genes tend to be between 3.5 kg and 4.5 kg heavier than those with the 'slimmest' possible genetic profile, the study of 90,000 people worldwide has found.
'The precise role in obesity of genetic variants in FTO and near MC4R remains to be discovered, but we can begin to understand the biological consequences of these variants,' The Times quoted lead researcher Ins Barroso as saying.
The discovery also illuminates the importance of 'junk DNA', 98 per cent of the genome that doesn't contain protein-making genes and was once thought to have no function. This junk contains genetic switches that turn gene activity up or down to influence protein manufacture.
According to the scientists, the new variant linked to obesity may be such a genetic switch -- it lies in a region of junk DNA, but very close to a gene called MC4R. Rare mutations in this gene cause early-onset obesity in a few children. The variant is thought to turn down expression of the MC4R gene.
The variant is significantly more common among people of Indian ancestry, a second study led by Jaspal Kooner of the Imperial College London has concluded.