An international team of researchers has identified the role of a gene which may explain why some people overeat and become obese.
Their research, published today in Public Library of Science Biology, showsthat the gene GAD2 has an appetite stimulating role, and that one form ofthe gene is strongly associated with obese people.
While the researchers recognise that obesity is a result of the interactionsof many genes and environmental factors, this is one of the first genes tobe strongly touted as a candidate 'gene for obesity'.
GAD2, which sits on chromosome 10, acts by speeding up production of aneurotransmitter in the brain called GABA, or gamma-amino butyric acid. WhenGABA interacts with another molecule named neuropeptide Y in a specific areaof the brain - the paraventricular nucleus of the hypothalamus - we arestimulated to eat.
The researchers behind the study believe that people who carry a moreactive form of the GAD2 gene build up a larger than normal quantity of GABAin the hypothalamus, and suggest that this over accumulation of GABA drivesthe stimulus to eat further than normal, and is thus a basis for explainingwhy obese people overeat.
Professor Philippe Froguel, senior author of the research, from ImperialCollege London, and Hammersmith Hospital, London, who carried out theresearch while at the Institut Pasteur de Lille, France, said: "Thediscovery that this one gene plays a role in determining whether someone islikely to overeat could be crucial in understanding the continued rise inobesity rates around the world."
"Genetic factors alone can not explain the rapid rise in obesity rates, butthey may provide clues to preventative and therapeutic approaches that willease the health burden associated with obesity."
He continued: "Having identified this gene, it may be possible to develop a screeningprogramme to identify those who may be at risk of becoming obese later inlife, and take effective preventative measures."
The team compared genome-wide scans of 576 obese and 646 normal weightadults in France, from which they identified two alternative forms, oralleles, of the GAD2 gene.
One form of the gene was found to be protective against obesity, whileanother increased the risk of obesity. The normal weight group of Frenchadults had a higher frequency of the protective form of the GAD2 gene.Obesity is three to five times less prevalent in France than in the USA.
In addition to the genome-wide scans, the obese patients also completed aneating habits questionnaire, measuring dietary restraint, disinhibition andperceived hunger. The results showed that those carrying the GAD2 allelethat increases the risk of obesity were significantly more likely to revealan inability to control their food intake, and perceive high levels ofhunger.