Girls 'more likely to be overweight by seven'

Nearly one in four (23 per cent) girls are too heavy at this age compared with just over one in six (18 per cent) boys, according to a study by the Institute of Education.

Researchers analysed the weights of 11,000 children taking part in the Millennium Cohort Study – which is tracking children born between 2000 and 2002.

The findings show that as well as gender, the number of brothers and sisters a child has is also an indicator of obesity.

Seven-year-olds who are only children are 25 per cent more likely to be overweight than those with one sibling and 30 per cent more likely to be overweight than those with two.

The study also found that youngsters aged five who are overweight are 25 times more likely than children of normal weight to still be too heavy two years later.

Youngsters with an overweight or obese mother, obese father and a mother who smokes are also likely to be heavier.

Principal author Dr Alice Sullivan said: "Girls and only children are more likely to become overweight between the ages of five and seven. It is not clear whether the increased risk for girls is due to them being overfed compared to boys, or because they are involved in less physical activity...or some combination of the two.

"Similarly, we do not know whether only children are less active due to lack of siblings, or overfed by indulgent parents. Either way, making parents aware of the increased risk to girls and only children may help to modify their behaviour."