Higher Body Fat Linked to Gene

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April 13, 2007 — British gene hunters said they have found the strongest DNA marker yet for obesity, and one that is very common among most Europeans.

The investigators first identified the gene, FTO, in the DNA of people with type 2, or late-onset diabetes, a condition that is lifestyle-related.

They were surprised to find the marker was associated with increased body fat rather than insulin production, so they scoured other DNA databases to see if the gene predisposed a person to obesity.

The results of that inquiry, the largest such undertaking of its kind to date, revealed that a variant of FTO was closely correlated with obesity, which has emerged as a major public health challenge in many developed nations.

The study showed that half of white Europeans carry one or more variants in their DNA, the researchers said.

Individuals with one copy of the FTO variant had a 30 percent higher risk of being obese than people without it.

In people with two copies of the "fat" gene, the risk rose to 67 percent, and they packed an additional 6.6 pounds in fat on average compared to people without any copies of the allele.

"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 is clearly a component to obesity that is genetic," said professor Andrew Hattersley, of the Peninsula Medical School, Exeter, and study co-author.

It's not clear why the gene predisposes people for increased body fat and higher rates of obesity, but it opens new avenues of investigation for researchers looking into obesity and related problems such as heart disease and diabetes, the researchers said.

"Even though we have yet to fully understand the role played by the FTO gene in obesity, our findings are a source of great excitement," said professor Mark McCarthy of Oxford University. "New scientific insights will hopefully pave the way for us to explore novel ways of treating this condition."

The researchers have only looked at one ethnic group so far -- white Europeans from Britain, Finland, Italy and northern Europe — but they are confident that the findings will hold up in other populations given the scope of the study.

Investigators examined the DNA of 39,000 people, more than 10 times the number used in a comparable earlier study.

The hope is to examine the DNA of African Americans and South Asians next, the investigators told journalists in a conference call. Problems with obesity and excess weight have been documented in both populations.

The study was a collaborative effort involving 24 geneticists in Britain. The project was funded by the Wellcome Trust, the Britain's largest medical research charity.