Obesity in children is largely genetic, say scientists

A group of UK scientists has confirmed that there are genetic links to child obesity. The researchers, from the Cancer Research UK Health Behaviour Research Centre at University College London, studied 5,092 pairs of twins aged between eight and 11. They looked at identical twins, who have exactly the same genes, and non-identical twins, who share only half of their genes. The scientists analysed measurements of waist circumference and Body Mass Index (BMI), which is the standard measurement for obesity, calculated by dividing a person's weight in kilograms by the square of their height in metres.

Since the pairs of twins were born at the same time and raised in the same household, they share broadly similar environments. The scientists could therefore work out the extent to which environmental factors influence a child's weight compared to the genetic influence. They reported in the American Journal of Clinical Nutrition that the variation was 77 per cent attributable to genetic factors and only 23 per cent to the environment in which they grow up.

Children who are overweight are more likely to become overweight or obese in adulthood. Adult obesity is linked to many diseases, such as heart disease, stroke and diabetes, and is also a major risk factor for certain types of cancer. According to government figures, obesity in children aged between two and ten has risen seven per cent in the last decade.

Dr John Wardle, who led the study, says that based on the findings it is 'wrong to place all the blame for a child's excessive weight gain on the parents - it is more likely to be due to the child's genetic susceptibility'. He goes on to stress that 'the results do not mean that a child with a high complement of susceptibility genes will inevitably be overweight, but that their genetic endowment gives them a stronger predisposition'.

Anti-obesity campaigners say that regardless of genes, a balanced diet and exercise are vital to good health. Sara Hiom, Cancer Research UK's director of health information, stressed that although the gene pool will not have changed dramatically over the last few decades, child obesity has increased, which means environmental factor are still partly to blame. She said: 'this research highlights the importance of doing all we can to encourage children to eat healthily. If genetic influence is strong, we must try to counter these inherited tendencies by providing the healthiest possible environment, and educating parents on the importance of a well-balanced diet and an active lifestyle'.