WASHINGTON Researchers have produced the first clear evidence for a gene common in the population that dictates why some people gain weight while others do not.
They found the gene, called FTO, by studying nearly 39,000 white Europeans in a finding they hope can lead to new ways to fight this growing global health problem.
British researchers, writing in the journal Science on Thursday, said the presence of a version of FTO increased a person's risk for obesity, and it was very common in the people studied -- 63 percent had one or two copies of it.
People with two copies had about a 70 percent higher risk of being obese than people with none and were an average of nearly 7 pounds (3 kg) heavier than a similar person with no copies. Those with one copy had a lesser but still elevated risk.
Genetics has long been assumed to play a role in making some people fatter than others, and previous research had tentatively implicated specific genes.
However, the researchers emphasized, genetics alone cannot fully account for a worldwide surge in obesity in recent decades that experts attribute to multitudes of people eating too much of the wrong foods and getting too little exercise.
Obesity is recognized as a growing public health problem worldwide. Obese people are at greater risk for diabetes, heart disease, stroke, high blood pressure and some cancers.
The researchers said that while improving one's lifestyle is still the key to reducing the obesity epidemic, their findings explain why some people will find it harder to change their weight than others because of their genes.
Researchers led by Andrew Hattersley of the Peninsula Medical School in Exeter and Plymouth and Mark McCarthy of the University of Oxford examined the genetics of nearly 39,000 children and adults from Britain, Finland and Italy.
They found 47 percent had one copy of the variant of the FTO gene and 16 percent had two copies.
The gene's effect was seen by the age of 7, they said.
'REGULATION OF WEIGHT'
"What this study has identified is a genetic variant which is involved in the regulation of weight," Hattersley said in a conference call with reporters. "And the critical role that it plays is in predisposing how much fat people have."
"Although this is the first gene that's been found that plays this kind of role," McCarthy said, "this isn't the whole story."
McCarthy said while extra body fat can be attributed to the presence the gene variant, this gene alone will not explain why some people are, for example, 110 pounds (50 kg) heavier than other people living in similar conditions in the same place.
The researchers said they do not know what the gene actually does to predispose people to obesity.
The researchers said they hope knowledge of the gene's role can lead to new ways of treating and preventing obesity. They said they hope to look at FTO in a more diverse population, including, for example, people from South Asia and U.S. blacks.
The World Health Organization estimated that 1.6 billion adults worldwide are overweight and at least 400 million adults are obese, according to the U.N. agency's definitions. It projected that by 2015, there will be about 2.3 billion overweight adults and more than 700 million obese adults.
Once seen as a problem exclusive to high-income countries, obesity is now on the rise in low- and middle-income countries, particularly in urban areas, the agency said.