Obese have higher levels of 'hunger hormone' in their blood
Researchers have discovered how a gene long associated with obesity makes people fat by triggering increased hunger, according to a new study published in the Journal of Clinical Investigation on Monday.
The finding could lead to new ways to fight the growing problem of obesity worldwide.
A series of tests led by a British research team found that people with a variation in the FTO gene had higher levels of the "hunger hormone" ghrelin in their blood, as well as increased sensitivity to the ghrelin in their brains.
An estimated one in six people have this common variation, which makes them 70 percent more likely to become obese.
"It's a double hit," said study leader Rachel Batterham from University College London.
The discovery follows studies of blood samples taken from volunteers after meals, combined with functional magnetic resonance imaging of their brains and cell-based studies that looked at ghrelin production at a molecular level.
Because some experimental drugs are known to suppress ghrelin, and could be particularly effective if targeted at patients with the obesity-risk variant of the gene, Batterham said the study provided new insights and possible new leads for treatment.
Earlier research has demonstrated that ghrelin can be reduced by eating a high-protein diet.
While the FTO gene only explains a small part of the obesity epidemic, this latest study was "an important step forward" in unraveling the various factors involved, said Steve Bloom of Imperial College London, although he was not involved in the study.
Obesity has reached near epidemic proportions around the globe, rising at alarming rates in developed and developing countries. The problem has also increased rates of diabetes, heart disease and certain cancers.
Being obese or overweight kills at least 2.8 million adults die each year. According to the World Health Organization, over 40 million children under 5 were overweight in 2011.
Although new medicines for obesity are available, developing effective treatments has proven challenging for pharmaceutical companies. After a decade-long lapse, for example, only two new obesity drugs have been approved by the FDA in the U.S., neither of which received approval until last year.
Other obesity drugs have been delayed, including the launch of Belviz from Arena Pharmaceuticals pending a final classification on its risk of abuse, and sales of Osymia from Vivus have been disappointing.
SOURCE: Journal of Clinical Investigation, “A link between FTO, ghrelin, and impaired brain food-cue responsivity” (July 15, 2013), doi:10.1172/JCI44403