UK researchers have discovered a commonly occuring gene variant that may explain why some people become overweight while others do not. However, they point out that it is unlikely to be the cause of the global obesity epidemic.
The findings are published in Science, the journal of the American Association for the Advancement of Science.
A UK research team, led by Dr Andrew Hattersley of Peninsula Medical School in Exeter, have discovered a gene variant that occurs in over half of people of European descent that they think helps to regulate the amount of fat in the body.
The scientists discovered the gene, known as FTO, in a study of 2,000 diabetics when they were doing a genome-wide search for susceptibility to type 2 diabetes. They found there was a strong link between the FTO variant and body mass index (BMI).
So they conducted another study on 13 cohorts of 38,759 Britons, Finns and Italians aged 7 and above where they found a similar link between the FTO variant and body weight.
The strength of the genetic influence depends on whether an individual has inherited one or two copies of the FTO gene variant.
A person with two copies of the FTO variant is likely on average to weigh 3 kilos (6.6 pounds) more than a person who does not have the FTO variant at all, and if they have only one copy they are likely on average to weigh 1.2 kilos (2.6 pounds) more.
About 16 per cent, or one sixth, of Europeans are likely to have both copies of the variant, according to the study. And around half will have one or two.
This is not to be confused with the estimated genetic predisposition to severe obesity which is around 1 in 10,000 people.
Commenting on the study, the team said it reinforces findings from twin studies that suggest obesity is driven partly by genes. However, they added that lifestyle and environment are also strong factors. The genetics has not changed in the last 100 years, but lifestyle and environment has, they said.
They are particularly excited by the fact this is the first study to identify a particular gene.
The scientists want to find out if other ethnic groups outside of Europe also have the FTO variant. They are planning to study the DNA of South Asians and black Americans because diabetes and obesity are more prevalent in these groups than the general population.
While the study did not help them work out the biological mechanism behind the FTO gene and weight control, they suspect it has to do with fat regulation. FTO is known to play a role in the hypothalamus which regulates appetite.
The World Health Organization (WHO) estimates that about 2 billion people worldwide are obese or overweight, that is about one third of all people over the age of 15. It also estimates that about 20 million children under 6 are in the same category.
“Once considered a problem only in high-income countries, overweight and obesity are now dramatically on the rise in low and middle-income countries, particularly in urban settings”, says the WHO.
There has been a mixed reaction to this study. Some are saying they hope this does not cause overweight people to be fatalistic about obesity and give up trying to get their weight down, while others say that this could mean people will be even more determined to take care of themselves if they think they have a genetic risk factor for obesity.
The impact on the research and development community is likely to be significant, with scientists curious to find out exactly what role FTO plays in fat regulation, and pharma companies looking at opportunites for new weight control drugs.
“A Common Variant in the FTO Gene Is Associated with Body Mass Index and Predisposes to Childhood and Adult Obesity.”
Timothy M. Frayling, Nicholas J. Timpson, Michael N. Weedon, Eleftheria Zeggini, Rachel M. Freathy, Cecilia M. Lindgren, John R. B. Perry, Katherine S. Elliott, Hana Lango, Nigel W. Rayner, Beverley Shields, Lorna W. Harries, Jeffrey C. Barrett, Sian Ellard, Christopher J. Groves, Bridget Knight, Ann-Marie Patch, Andrew R. Ness, Shah Ebrahim, Debbie A. Lawlor, Susan M. Ring, Yoav Ben-Shlomo, Marjo-Riitta Jarvelin, Ulla Sovio, Amanda J. Bennett, David Melzer, Luigi Ferrucci, Ruth J. F. Loos, Inês Barroso, Nicholas J. Wareham, Fredrik Karpe, Katharine R. Owen, Lon R. Cardon, Mark Walker, Graham A. Hitman, Colin N. A. Palmer, Alex S. F. Doney, Andrew D. Morris, George Davey-Smith, The Wellcome Trust Case Control Consortium, Andrew T. Hattersley, and Mark I. McCarthy.
Science Published Online April 12, 2007.
Written by: Catharine Paddock
Writer: Medical News Today