Two new studies have shown that alterations in a single gene are associated with severe obesity and 'binge-eating' behaviour in some people. A team at Cambridge University in the UK found that around five or six per cent of severely obese people studied inherited a particular version of a gene called MC4R. Another study, carried out by a team of US, Swiss and German researchers, also found an association between obesity, binge-eating behaviour and MC4R gene alterations. Both groups published their findings in this month's issue of the New England Journal of Medicine.
The MCR4 gene makes a brain protein called the melanocortin-4 receptor, which is abundant in an area of the brain thought to be involved in appetite control. Previous research found that mice that are missing the MC4R gene overeat and become obese, and it seems the same gene appears to cause unhealthy weight gain in humans. For this small group of people, the extra weight 'is not their fault' says Dr Joel F Habener, an obesity researcher who wrote an editorial accompanying the two research papers. 'They actually have an inherited disease' he added. One of the studies found that of 469 severely obese people, five per cent had a MC4R mutation, all of whom said they were binge eaters. In contrast, only 14 per cent of obese people who did not carry the mutation reported binge eating. However, not everyone who carries an MC4R mutation becomes obese, suggesting that other genes may block its effects, said Habener.
Another study, published in Nature last week, showed that different genes were responsible for obesity in different groups of genetically altered mice. Scientists at the University College of Los Angeles and US companies Rosetta Inpharmatics and Merck identified a 'hot spot' of obesity-related genes on mouse chromosome 2. The findings indicate that treatments for human obesity might vary for the different subtypes of the disease. Team leader Eric Schadt told BBC News Online that one group of people might be obese because of a gene that affects hunger perception, while another group might have a defect in their metabolic rate.
Sources and References
Study links binge eating to mutation in a gene
Some cases of obesity caused by a single gene
Study finds weak gene in binge eaters