People with mutations in the FTO
gene had higher levels of ghrelin in their blood, which made them feel hungry
soon after eating a meal, and could help to explain why they eat more and
choose higher-calorie foods.
Everyone has two copies of the
FTO gene, and the 16 percent of the population with genetic defects in both
copies have a 70 percent higher chance of being obese. Almost half of people
have one FTO gene mutation, and are 30 percent more likely to be obese.
Batterham from University College London, who led the study, explained: 'What
this study shows us is that individuals with two copies of the obesity-risk FTO variant are biologically programmed to eat more'. She added: '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'.
The study compared samples of
two groups of men of normal weight: one with two copies of the high-risk FTO
gene, and the other with two copies of the gene thought to cause low risk of
obesity. Although levels of ghrelin usually fall after eating and remove
feelings of hunger, blood samples revealed that the hormonal levels rose more
quickly after meals in the high-risk patients.
Additionally, a series of brain
scans in 24 men showed that these two groups responded differently to pictures
of food. Men with the high-risk genes found pictures of higher-calorie foods
more appealing than those with the low-risk variation.
Understanding how FTO affects
the odds of becoming obese could help patients manage their weight. Dr
Batterham said: 'We know that ghrelin, and therefore hunger, can be reduced by
exercise like running or cycling or by eating a high-protein diet'.
Bloom from Imperial College London commented on the results, saying: 'Slowly we are
discovering the factors which make us overweight and this study, encompassing
not only demonstration of a higher level of hunger hormone, ghrelin, but also changes
in the brain associated with ghrelin's action, is an important step
forward. Already pharmaceutical companies are working on ghrelin
antagonists and this will further spur on that effort and perhaps indicate whom
best to treat'.
These findings shed some light
on why people who have a variation of this gene are more likely to be obese — a
question that has been unanswered until now. However, NHS
Choices points out that 'this was a small study and the implications
of these findings are unlikely to have any immediate impact on solving the