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Scientists have discovered the clearest link yet between genes and obesity in a study that opens the way to explaining why some people put on weight while others remain slim.
The researchers have identified a genetic variation that gives a child a 70 per cent higher risk of developing obesity compared with a child who has not inherited the genetic variant.
Although the scientists cannot explain how the gene makes obesity more likely, they believe the discovery will start a race to find the fundamental reasons why some people are born with a predisposition to being fat.
"As a nation, we are eating more and doing less exercise, and so the average weight is increasing, but within the population some people seem to put on more weight than others," said Professor Andrew Hattersley from the Peninsula Medical School in Exeter.
"Our findings suggest a possible answer to someone who might ask: 'I eat the same and do as much exercise as my friend next door, so why am I fatter?"' There was clearly a genetic component to obesity, Professor Hattersley said.
The study investigated variations in the DNA of a gene known as FTO - short for "fatso" - which occur in patients with type-2 diabetes. More than 2000 diabetes patients and 3000 healthy "controls" took part in the study, published in the journal Science.
The scientists from the universities of Exeter, Plymouth and Oxford searched the genomes of the diabetes patients and found a strong association between the disease and a certain variant of the FTO gene.
When the scientists expanded the study to look at 37,000 other people without diabetes, they found the same variant was also strongly associated with being overweight.
Carrying one copy of the FTO variant imparted a 30 per cent increased risk of obesity compared with a person with no copies. Having two copies of the variant increased the risk to 70 per cent. About one in six white Europeans carry two copies.
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