After a decade of often overblown stories about one would-be 'fat gene' after another, scientists seem to have at last found the gene in question – one of them, that is. A group of researchers based in the U.S. and Germany pinned down what may be the first gene that is commonly connected with obesity in humans.
The study began at the Boston University School of Medicine, where researchers collected genetic data and body mass indexes from 923 participants in the 24-year Framingham Heart Study. Using a special high-throughput gene-mapping tool, they compared people's BMIs to 116,204 places in the genome that vary between people, and picked out the one that seemed most clearly correlated with obesity. They then worked with researchers in other groups to see if one variant at that spot was consistently associated with obesity; in four out of the five groups, it was. On average, the 10% of people with the more-likely-to-be-overweight version were about 1 BMI unit heavier than other people, and were 22% more likely to be obese, regardless of race or sex.
The discovery in no way ends the search for obesity genes. BU's Michael Christman, the senior author on the paper, estimates that there are about 8 other genes that significantly affect someone's chances of being obese. Scientists suspect that about half of obesity is determined by heritability, so Christman says the recently found gene is connected with about 5% of all obesity. The BU group hopes to find more obesity genes using the same method to root through the Framingham data. They say finding genes correlated with obesity could help researchers find out why people become overweight, and therefore suggest ways to fight it.
While this seems to be the first study that connects one genetic location with obesity common throughout the population, many previous papers – or news reports about them – have proclaimed discovery of other "fat genes." Many of these genes are truly connected with obesity, but are present only tiny, pathological fractions of the human population, and presumably unrelated to more generic obesity. Other studies have found genes that exist in all people and play a role in the actual formation or growth of fat cells.