A new study, published in the International Journal of Obesity, may explain why certain genetic variations increase a person's risk of obesity. Professor Jane Wardle and team at University College London, UK, have demonstrated associations between particular variants of the FTO gene, and the likelihood of overeating.
An international health burden, particularly in developed countries, obesity can increase the risk of several common and debilitating diseases, like heart disease, cancer and diabetes. Increasingly, it seems that obesity has a hereditary component.
In 2007, a study conducted by multiple UK-based labs screened the human genome for diabetes-susceptibility genes, concluding in the journal Science that a common variant in the FTO gene (for 'fat and obesity associated') predisposes to diabetes through an effect on body mass index. Sixteen per cent of adults who carried two copies of a 'high risk' variant weighed on average three kilograms more than non-carriers.
In last week's paper, the researchers designed a behavioural study that would test whether knowing when 'enough is enough' might be correlated with particular versions of FTO. 131 children, aged between four and five years of age, were offered a mix of sweet and savoury biscuits an hour after having eaten a meal. Those consistently reaching for more, although considered to be 'full', were found more likely to be carrying at least one copy of the high risk variant, compared to the less cookie-hungry kids, who carried two low-risk variants. The latter, the paper concludes, are 'protective against overeating by promoting responsiveness to internal signals of satiety'.
'This study showed that some children don't know when to stop', comments Professor Wardle, 'which could lead to the onset of obesity and a lifetime of health problems. Children with higher risk versions of the gene might be helped if parents do their bit to keep temptations out of the home'.
Obesity, like all complex physiological traits, is a multifactorial condition, in which multiple genes play a role. However, the interplay between genetics and the environment is key in such situations. By decreasing a child's 'sensitivity to satiety', one particular FTO variant appears to make a child more vulnerable to calorific temptations. However, says Sara Hiom, director of health information at Cancer Research UK, 'a genetic propensity to overeating doesn't doom a child to a lifetime of obesity'.