US researchers at the BostonUniversityMedicalSchool have identified the first common genetic variant in the human genome that substantially increases a person's risk of obesity. The study, led by Alan Herbert, is the first ever to strongly identify a genetic component linked to obesity in a number of populations.
The research team studied a sample of over 900 people and looked at almost 87,000 points in the human genome which showed variation between each individual. They then related these variations to each person’s BMI. They studied families from a long-running coronary study in Massachusetts, called the Framingham Heart Study. The team found In follow up studies involving approximately 9000 individuals the same association was found. They found that a single mutation in this particular region, from a G to a C, makes a person more prone to obesity. It is believed that this change somehow affects the regulation of the gene INSIG2, which plays a role in fat production.
‘The C variant was found to increase the risk of obesity in many populations including people of Western European ancestry, African Americans and children. About 10% of the populations studied carried two copies of this mutation. It was discovered that an individual with two copies of the C variant is 22% more likely to have a body mass index (BMI) greater than 30, which is the point where people move from being classified as ‘overweight’ to ‘obese’. People with two copies of the C variant were about 1 BMI unit heavier than other individuals’ (1). This is only a relatively small difference in weight compared to those with one or no copies of this variant, however this promotes the idea that the genetic variant simply tips people from being overweight to obese. Never the less some scientists predict that genes may contribute anywhere from 30% to 70% of the risk of obesity. They also stress that environmental factors, like diet and exercise, play an extremely crucial role. It is hoped that this discovery will open doors to new linkages and thus treatments for the obesity condition.
