The genetics of overeating

Children with a "high-risk" version of FTO eat more biscuits after a meal.

You’ve just eaten a big meal and someone plops a plate of biscuits in front of you. Do you eat them? And if so, how many would you scoff? According to a new study, one of your genes could affect your answer to these questions.

The gene in question is called FTO and it was the first to be conclusively linked to obesity. One small change separates two versions of the gene – a “low-risk” version and a “high-risk” one.

Two years ago, scientists found that people who have one high-risk copy are 30 per cent more likely to be obese than those without any. And people saddled with two high-risk copies are 70 per cent more likely to be obese.

At that point, the gene’s function was largely a mystery. But new research from Cancer Research UK scientists, published this week, has suggested that it affects how full people feel after a meal, and thus their ability to stop eating.

The new study was led by Jane Wardle, director of Cancer Research UK’s Health Behaviour Research Centre at UCL, and published in the International Journal of Obesity. Her team recruited 131 children aged between four and five and gave them a plate of biscuits after they had just eaten a meal.

They found that children with one or two copies of the high-risk version of FTO ate more of these biscuits than those who lacked either copy. And that was the case across different weight categories – the gene had an influence regardless of whether the children were lean or overweight.

Obviously, FTO isn’t the whole story when it comes to overeating. There are probably many more obesity-related genes and the high-risk FTO version only has a small effect on behaviour. Even so, its influence is widespread. In Professor Wardle’s study, half of the children had just one copy of the high-risk variant and another 20 per cent had two copies.

This is a classic case of nature and nurture working hand-in-hand. A child’s risk of overeating is influenced by both their genes (whether they have high-risk versions of FTO) and their environment (whether they were given biscuits after the meal). Their genes shaped their responses to the world around them.

This is a critical point – as we’ve discussed before, obesity-related genes do not doom children to a future of overeating. Habits, of course, can be changed, but studies like these could eventually help us to identify children who are at greatest risk of putting on weight and who need the most help to avoid doing so.

And why is this relevant to cancer? Simply because putting on too much weight is one of the most important causes of cancer outside of smoking.

Several types of cancer are more common in overweight and obese people, including breast cancer after the menopause, and cancers of the bowel, womb, oesophagus, pancreas, gallbladder and kidney. That list includes two of the most common cancers and three of the hardest to treat.

Ed

Reference:

J Wardle, C Llewellyn, S Sanderson, R Plomin (2008). The FTO gene and measured food intake in children International Journal of Obesity, 33 (1), 42-45 DOI: 10.1038/ijo.2008.174

Image by Jusben at Morguefile