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Scientists have discovered a new link between obesity and genetics, finding that certain people have higher levels of a hormone that makes them hungry.
We already know that one in six people are affected by a variation in a particular obesity-associated gene called FTO, but this University College London study showed exactly how the gene affects people. These people had higher levels of a hormone called ghrelin, which triggers hunger in the body. They were also more sensitive to ghrelin in their brains, which affected their behaviours around eating and control.
The findings explain why people affected by this gene variation eat more and prefer kilojoule-dense foods, even when they are not overweight.
"We've known for a while that variations in the FTO gene are strongly linked with obesity, but until now we didn’t know why,” said Dr Rachel Batterham, who led the study.
“What this study shows us is that individuals with two copies of the obesity-risk FTO variant are biologically programmed to eat more. Not only do these people have higher ghrelin levels and therefore feel hungrier, their brains respond differently to ghrelin and to pictures of food – it’s a double hit.”
These behaviours were observed in people from adults to preschool-aged children. The scientists involved in the study hope to use this information to equip them to fight obesity in the long term.
“At a therapeutic level this arms us with some important new insights to help in the fight against the obesity pandemic,” Dr Batterham said.
“For example, we know that ghrelin (and therefore hunger) can be reduced by exercise like running and cycling, or by eating a high-protein diet. There are also some drugs in the pipeline that suppress ghrelin, which might be particularly effective if they are targeted to patients with the obesity-risk variant of the FTO gene.”
Because ghrelin is produced largely in the stomach, scientists long hypothesised that any procedure that decreases the physical size of the stomach would in turn decrease the production of this hormone. In 2002, this was proven to be true in the case of gastric bypass surgeries, after scientists tested the hormones of obese patients before and after surgery. They also compared the hormones with those of people who had lost weight by means of diet.
Published in the New England Journal of Medicine, the study found that gastric bypass surgery was far more effective in controlling hunger and resulted in “markedly suppressed ghrelin levels”, which contributed to the dramatic weight loss observed in patients.
IMAGE CREDIT: Eric May