MORE than half of a child’s Body Mass Index showing how fat or thin they are can be inherited from their parents, a new study has found.

Research at the University of Sussex shows that on average 30 to 40 percent of our BMI comes from our parents and for the most obese children the proportion rises to 55-60 per cent.

This suggests that more than half of their tendency towards obesity is determined by genetics and family environment.

The study, led by the university, used data on the heights and weights of 100,000 children and their parents spanning six countries worldwide: the UK, USA, China, Indonesia, Spain and Mexico.

The researchers found that the intergenerational transmission of BMI (Body Mass Index) is approximately constant at around 0.2 per parent - i.e. that each child’s BMI is, on average, 20 per cent due to the mother and 20 per cent due to the father.

The pattern of results, says lead author Professor Peter Dolton of the University of Sussex, is remarkably consistent across all countries, irrespective of their stage of economic development, degree of industrialisation, or type of economy.

Professor Dolton said: “Our evidence comes from trawling data from across the world with very diverse patterns of nutrition and obesity – from one of the most obese populations – USA – to two of the least obese countries in the world – China and Indonesia. This gives an important and rare insight into how obesity is transmitted across generations in both developed and developing countries.

“We found that the process of intergenerational transmission is the same across all the different countries.”

The findings are published in the journal Economics and Human Biology.

The study also shows how the effect of parents’ BMI on their children’s BMI depends on what the BMI of the child is. Consistently, across all populations studied, they found the ‘parental effect’ to be lowest for the thinnest children and highest for the most obese children. For the thinnest child their BMI is 10 per cent due to their mother and 10 per cent due to their father. For the fattest child this transmission is closer to 30 per cent due to each parent.