A gene variant common in the European population has been discovered that shows the first clear link to obesity, researchers say.

The gene, called FTO, was found by studying the genome of 39,000 white people in the United Kingdom, Finland and Italy who gave blood samples, the team said in Thursday's online issue of the journal Science.

People who had two altered copies of the gene were about three kilograms heavier on average, and had a 70 per cent higher risk of obesity than people with no copies of the gene. Those with one copy had a lesser but still elevated risk of having a higher fat mass.

About 63 per cent of people surveyed had one or two copies of the mutation, and the effects of the gene were seen by age seven, said the researchers, who set out to look for genes that increase susceptibility to Type 2 diabetes. 

"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?' said Prof. Andrew Hattersley from the Peninsula Medical School in Exeter, England.

"There is clearly a component to obesity that is genetic."

Tackling rise in obesity

The researchers said they do not know why people with copies of the FTO mutation put on more weight, because the function of the gene is unknown. For example, it may cause people to store fat more efficiently.

By identifying the genetic link, the researchers said they hope to explore new ways of treating obesity, such as drugs that target the gene. They also aim to look for the FTO gene in South Asians and blacks, since finding it in more than one population would make genetics researchers more confident about the link.

Of the participants in the study, about 25 per cent were considered obese, based on their body mass index, a relationship between height and weight.

Role of environment

Genes alone are unlikely to be a major factor behind surging obesity rates, since genetic changes do not happen on a scale of 20 to 30 years, scientists say.
 
The obesity rate among Canadian boys jumped from two per cent to 10 per cent in the last 15 years, and from two per cent to nine per cent among girls, according to guidelines published earlier this week in the Canadian Medical Association Journal.

Poor diet, lack of exercise and genetics all contribute to the problem, said Dr. Glenn Berrall, head of the pediatric nutrition clinic at North York General Hospital in Toronto.

"We seem to be living in an environment that fosters excess weight," Berrall told CBC Newsworld on Thursday.

Factors include:

• Lack of opportunities for physical activity in school or in daily life.
• Ease of transportation.
• Perceptions of unsafe environments and neighbourhood designs that deter walking.
• Easy and frequent access to high-calorie foods.

All levels of society and governments have a role to play, such as offering nutrition labelling, school nutrition and physical activity programs, and healthy role models from parents, Berrall said.

Last fall, the International Congress on Obesity heard that more than 1.5 billion adults and 10 per cent of children are overweight or obese. The excess pounds increase the risk for heart disease, Type 2 diabetes, high blood pressure and some cancers.