Nature is more important than nurture in determining whether a child will become overweight, a new study reports today (Thursday) in the American Journal of Clinical Nutrition.

Lead author Professor Jane Wardle, director of Cancer Research UK’s Health Behaviour Research Centre, looked at over 5000 pairs of twins, and found that variation in children’s body mass index (BMI) and waist circumference were 77 per cent attributable to genes and 23 per cent attributable to the environment in which the children were growing up.

Child weight is of great concern because children who are overweight are likely to become overweight or obese adults and this can contribute to ill health and increase cancer risk in later life. Obesity has been linked to a range of cancers including breast, womb and kidney.

The study was funded by Cancer Research UK, the Medical Research Council and the Biotechnology and Biological Sciences Research Council.

Professor Wardle, who is based at University College London, said: “We looked at identical pairs of twins who share all their genes and compared their measurements with non-identical pairs of twins who only share half their genes. Contrary to the widespread assumption that family environment is the key factor in determining weight gain, we found this was not the case.

“This study shows that 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.

“These results do not mean that a child with a high complement of ‘susceptibility genes’ will inevitably become overweight, but that their genetic endowment gives them a stronger predisposition. In today’s environment – which provides unprecedented opportunities for all children to overeat and be sedentary – it is not surprising these tendencies result in weight gain.”

“It is therefore especially important to provide to best possible environment for all children to help protect those who are at higher genetic risk.”

Sara Hiom, Cancer Research UK’s director of health information, 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.

“Parents of children who show early weight gain may need additional support to provide the best context for their children to grow up healthy.

“We know that obesity is an important risk factor for a number of cancers so it is important for us all to do what we can to reduce our risk of the disease by eating healthily and maintaining an active lifestyle to avoid being overweight or obese.”

For media enquiries contact the Cancer Research UK press office on 020 7061 8300 or, out-of-hours, the duty press officer on 07050 264059.


Evidence for strong genetic influence on childhood adiposity despite the force of the obesogenic environment. Jane Wardle et al. 2008. American Journal of Clinical Nutrition.

Obesity, bodyweight and cancer

Maintaining a healthy body weight is one of the best ways to reduce your chances of getting cancer, after quitting smoking.

Being very overweight (obese) increases your risk of cancer of the womb, kidney, colon, gallbladder and oesophagus (foodpipe). It is also linked to breast cancer in women who have gone through the menopause.

Reduce the risk.

More than half all cases of cancer can be prevented according to Cancer Research UK’s Reduce the Risk campaign. The campaign’s key messages are:

  • Stop smoking: It’s the best present you’ll ever give yourself.
  • Stay in shape: Be active and keep a healthy body weight.
  • Eat and drink healthily: Limit alcohol and choose a balanced diet with plenty of fruit and vegetables.
  • Be SunSmart: Protect yourself in the sun and take care not to burn.
  • Look after number one: Know your body and see your doctor about anything unusual. Go for screening when invited.

About Cancer Research UK

  • Together with its partners and supporters, Cancer Research UK’s vision is to beat cancer.
  • Cancer Research UK carries out world-class research to improve understanding of the disease and find out how to prevent, diagnose and treat different kinds of cancer.
  • Cancer Research UK ensures that its findings are used to improve the lives of all cancer patients.
  • Cancer Research UK helps people to understand cancer, the progress that is being made and the choices each person can make.
  • Cancer Research UK works in partnership with others to achieve the greatest impact in the global fight against cancer.
  • For further information about Cancer Research UK’s work or to find out how to support the charity, please call 020 7009 8820 or visit our homepage.


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