The lifestyle of parents - rather than their genes – is mainly responsible for their children being overweight, say researchers.

A new study of adoptive children shows inherited factors are far less important in creating weight problems than the environment where they grow up, including the parents’ diet and exercise habits.

The researchers compared the bodyweight of thousands of biological and adopted children to that of their parents.

They found that when both adoptive parents are overweight, the likelihood of an adopted child being overweight is up to 21 per cent higher than when the parents are not overweight.

Because these children are adopted their weight problems can be largely attributed to their parents’ lifestyles rather than their genes.

In comparison, children who have two biological parents who are overweight were found to be 27 per cent more likely to be overweight – just six percentage points more than adopted children, showing the relatively small influence of genetics.

The research was carried out by experts at the Centre for Economic Performance, based at the London School of Economics and Political Science (LSE).

Lead researcher Dr Joan Costa Font, Associate Professor of Political Economy at LSE, said ‘The good news is that our research shows that we can do something about children’s weight problems.

‘Although initiatives that target schools and children themselves are admirable, our results suggest that the primary focus should be on helping parents adopt healthier lifestyles and be better role models concerning healthy eating and physical exercise.’

The data came from the Health Survey for England’s (HSE) children’s surveys 1997- 2009.

Altogether 13,536 ‘observations’ of bodyweight were made of parents and their natural children and 300 observations of parents and adopted children.