Researchers from the Medical Research Council and the University of East Anglia looked at children's social and ethnic backgrounds, school and home environments.
The diet, physical activity and body shape of over 2,000 nine and 10-year-olds from schools in Norfolk were studied. "We wanted to better understand why some children have a healthier lifestyle than others," said a representative.
Only half of the children said they ate any fruit or vegetables. Fewer boys ate healthy food than girls but more unhealthy snacks. Children from more affluent backgrounds were more likely to eat fruit and vegetables every day.
One of the authors, Dr Simon Griffin, said the findings suggested fruit and vegetable promotions should target children from lower socio-economic backgrounds. He welcomed findings that almost 70 per cent of the children met national physical activity guidelines but warned: "There's uncertainty whether this is enough activity to stave off risk factors for diabetes and cardiovascular disease later."