London, Feb 20 (IANS): Worried about your kid's ever increasing waistline? Blame your level of obesity, as according to a new study, kids are nearly 35-40 per cent likely to inherit the body mass index (BMI) -- how fat or thin they are -- from their parents.

The findings showed that for children who are in the heavy obese category, the proportion rises to 55-60 per cent, suggesting that more than half of their tendency towards obesity is determined by genetics and family environment.

Conversely, the 'parental effect' was found to be the lowest for the thinnest child, as opposed to being the highest for the most obese child.

For the thinnest child their BMI is 10 per cent due to their mother and 10 per cent due to their father, whereas, for the fattest child this transmission is closer to 30 per cent due to each parent.

"This shows that the children of obese parents are much more likely to be obese themselves when they grow up - the parental effect is more than double for the most obese children as compared to what it is for the thinnest children," said lead author Peter Dolton, Professor at the University of Sussex in Britain.

For the study, published in the journal Economics and Human Biology, the team used data on the heights and weights of 100,000 children and their parents spanning six countries worldwide: the Britain, US, China, Indonesia, Spain and Mexico.

The results showed that the intergenerational transmission of BMI 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.

"These findings have far-reaching consequences for the health of the world's children. They should make us rethink the extent to which obesity is the result of family factors, and our genetic inheritance, rather than decisions made by us as individuals," Dolton noted.