'Fat gene' linked to adult obesity and impulsive eating

A common genetic mutation linked to childhood obesity also increases the likelihood of becoming overweight in adulthood, scientists have discovered. They found the genetic variation also increases impulsive eating as well as a person's appetite for fatty foods.

The study, published in Molecular Psychiatry, analysed the behaviour, weight and brain activity of 700 people. This revealed that a variation of the FTO gene found in 45 percent of the participants was linked to an increased body mass index.

Brain scans also revealed that people with the obesity-related FTO variant showed reduced brain activity in the medial prefrontal cortex, which has a role in controlling impulses as well as choice of food.

'People who carry one or two copies of the FTO variant show increased intake of high-calorie or fatty food as they age', Dr Madhav Thambisetty, chief of clinical and translational neuroscience at the US National Institute of Ageing, and lead author of the paper, told HealthDay.

The effect appeared to increase with the number of copies of the variant. 'We see a dose effect, where these changes in impulsivity or a preference for fatty foods increase with multiple copies of the gene', Dr Thambisetty said.

This change in brain activity could provide clues as to how the FTO gene contributes to obesity. 'Many studies have tied certain versions of the FTO gene to chronic obesity, but doctors have struggled to determine why the gene affects a person's risk of obesity', Professor Ruth Loos, from Mount Sinai Hospital, New York, who was not involved in this study, told HealthDay.

She added: 'These types of studies are important to disentangle the mechanism of why FTO is associated with obesity, but it's only one piece of a huge puzzle'.

While increasing the chances of developing obesity, the variant of the FTO gene does not guarantee that someone will become overweight. The study authors highlight previous studies demonstrating that exercise can still overcome the increased risk of obesity posed by the FTO variant.

Dr Steven Lamm, medical director of the Tisch Center for Men's Health at Langone Medical Center in New York City and not connected to this study, told HealthDay: 'This should not be an excuse, but it has to be a partial explanation why intelligent and motivated individuals struggle so much, because they are fighting their biology and it's uncomfortable to fight your own biology'.