British researchers have discovered an obesity gene that may help explain why some people get fatter than others. But as we hear from VOA's David McAlary in Washington, they say it is not alone responsible for the epidemic of weight gain sweeping the globe.
The World Health Organization estimates that about two billion people around the world are overweight or obese, that is about one third of the population above the age of 15. Also in this category are 20 million children five and under. Obesity's role in diabetes, cancer and other diseases makes it one of the most pressing health problems.
Now, researchers have found the first clear genetic reason that explains, in part, why some people weigh too much and others remain trim. A British team, led by physician Andrew Hattersley of Peninsula Medical School in Exeter, reports in the journal Science that it has located a gene mutation in more than half of all people of European ancestry that helps regulate weight.
"The critical role that it plays is in predisposing to how much fat people have," he said. "Approximately one-sixth of the [white] population will have two copies of the variant, and that will result in them being, on average, three kilograms of fat heavier than the one-third of the population who do not have any copies of the variant."
Hattersley's group came across the gene while examining the DNA of 2,000 British adult diabetics. Obesity is a major risk factor for adult diabetes, and further study showed the scientists that the mutation was associated with weight differences in the diabetics.
To see if it affected non-diabetics, they tested DNA in blood samples from 37,000 British, Finnish and Italian people aged seven and older. Study collaborator Mark McCarthy of the University of Oxford says the same genetic variant affected their weight, too.
"This clearly reinforces the early suspicions we had from twin and other data that obesity was a condition that was partly genetically driven, but also clearly influenced by environment and lifestyle," he said. "But, until now, it has not really proven possible to finger particular genes as being responsible for that genetic component, and that is really what this study has done."
The researchers plan to find out if the gene, called FTO, is present in other ethnic groups besides caucasians. They will look specifically at the DNA of South Asians and black Americans, who have a higher incidence of adult diabetes and other obesity-related diseases than the general population.
They say they do not yet know biologically how the FTO gene affects weight, but point out that it is not to blame for the majority of the weight gain around the world. Hattersley says overeating and less physical activity are the major factors.
"Whenever you think about how much obesity is there, that will not be explained by genetics, because genetics is the same as it was 100 years ago when we had far less obesity," he said.
Still, the scientists say having the gene variant could explain why some people have a harder time losing weight than others. They hope the finding can lead to new ways of treating and preventing obesity.