There is a strong link in obesity between mothers and daughters and fathers and sons, but not across the gender divide, research suggests.
A study of 226 families by Plymouth's Peninsula Medical School found obese mothers were 10 times more likely to have obese daughters.
For fathers and sons, there was a six-fold rise. But in both cases children of the opposite sex were not affected.
The researchers believe the link is behavioural rather than genetic.
They say the findings mean policy on obesity should be re-thought.
Researchers said it was "highly unlikely" that genetics was playing a role in the findings as it would be unusual for them to influence children along gender lines.
Instead, they said it was probably because of some form of "behavioural sympathy" where daughters copied the lifestyles of their mothers and sons their fathers.
It is because of this conclusion that experts believe government policy on tackling obesity should be re-thought.