Genetics and heritability may account for 77 per cent of obesity, while environmental factors make up less that 25 per cent, suggests new research.
The study, by University College London (UCL) researchers, followed 5,092 pairs of twins and highlights the complexity of the obesity issue. The report, "Evidence for a strong genetic influence on childhood adiposity despite the force of the obseogenic environment", appears this month in the American Journal of Clinical Nutrition.
A lot of focus has been placed recently on the food industry to reformulate their products, provide clear labelling and reduce advertising to children. Instead of viewing this study as a get-out clause, the food industry, government and health charities have responded with similar acceptance of the part they play in beating the spread of obesity.
"The UK food and drink manufacturing industry takes the dietary needs and health of all its consumers very seriously," said Keren McCarron from the UK's Food and Drink Federation (FDF). "There is no silver bullet that can be fired at the complex issue of obesity."
The study Twin studies are a good way for determining genetic and environmental influences of health and behaviour as monozygotic twins (identical genes) can be compared with dizygotic twins (non-identical, sharing half the genes).
The researchers analysed the body mass index (BMI) and weight circumference (WC) in a UK sample of 5,092 twin pairs aged eight to 11 years, born between 1994 and 1996. The results showed that the monozygotic correlations were similar in boys and girls, and greatly exceeded those of the dizygotic twins, suggesting a strong genetic influence.
Researchers concluded therefore that adiposity heritability amounts to 77 per cent for BMI and 76 per cent for WC. Shared environment effects were 10 per cent for both, and non-shared environment effects were 13 per cent and 14 per cent respectively. The report's author wrote: "Although contemporary environments have made today's children fatter than were children 20 years ago, the primary explanation for variations within the population, then and now, is genetic difference between individual children."
Responsibility Obesity is clearly a multifaceted issue, with many contributing factors, and requires a combination of solutions.
Professor Wardle at UCL said: "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."
With approximately 1.6bn adults overweight worldwide and 400m obese, according to the World Health Organisation, the study shows the importance of providing nutritional food, to counterbalance the effect of genetics and help those who are more susceptible to obesity. "We all - industry, the rest of the food chain, government, regulators and educators - have a responsibility in tackling this problem, and the food and drink manufacturing industry has long been committed to playing a positive role in improving the health of the nation," said McCerron from the FDF.
Food manufactures have demonstrated dedication to helping curb obesity through reformulation and embracing new labelling concepts to provide clear information to consumers on the nutritional value and fat content of their products. McCerron added: "A recent survey of FDF members revealed that the recipes used for at least £15bn worth of foods have less fat, sugar and salt, compared with 2004. In addition, a further £11.5bn worth of products have been launched as 'lower in' versions."
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. Source: American Journal of Clinical Nutrition February 2008, Volume 87, No. 2, Pages 398-404
"Evidence for a strong genetic influence on childhood adiposity despite the force of the obseogenic environment"
Authors: J. Wardle, S. Carnell, C. Haworth, R. Plomin