Researchers at Trinity College Dublin have found stark socio-economic inequalities in children's body mass index (BMI).

These emerge during the pre-school years and "widen" across childhood and into early adolescence.

These findings are from a study published in the international journal Paediatric and Perinatal Epidemiology.

Data on height and weight - or BMI - was analysed from 41,399 children measured over time in three European countries - Ireland, the UK and Portugal.

This used the mother's highest level of education as a marker of socio-economic position.

The research showed that whilst there were no differences in BMI between children grouped by their mothers education in infancy, differences in BMI emerged by pre-school age (three to five years) - with children from primary and secondary educated maternal backgrounds gaining body mass at a faster rate compared with children from tertiary educated maternal backgrounds.

These differences continued to widen as the children aged in all three countries.

The authors used International Obesity Task Force (IOTF) cut-offs to determine how these differences in BMI translate into overweight and obesity.

In general, they found that children from primary educated backgrounds were more likely to be overweight or obese at any age, compared with children whose mothers' had a tertiary level education.

"This is a worrying trend as children who are obese in early life are more likely to maintain this status into adolescence and adulthood, increasing risk for chronic disease later in life", the resrearchers said.

"A heavier burden of disease"

In Ireland, boys and girls whose mothers' had a primary-level education measured 0.90 kg / m2 and 1.31 kg / m2 heavier, on average, respectively at 13 years of age compared with children from tertiary-level (i.e. university) backgrounds.

Dr Cathal McCrory is the lead author of the paper, and a research assistant professor at Trinity College.

"This study shows that children from disadvantaged socio-economic backgrounds gain body mass more quickly than their more advantaged peers, are more likely to be overweight or obese from pre-school age onwards, and are more likely to become obese if previously non-overweight.

"They are quite literally carrying a heavier burden of disease from much earlier in life.

"These findings reinforce the necessity of challenging the childhood obesity epidemic at early ages as these patterns are difficult to change once they have become entrenched.

"Urgent government action is now required to understand the material, social, and structural barriers that contribute to these stark socio-economic differences in obesity risk".

The findings arise from Trinity's involvement with the LIFEPATH project, an EU-funded consortium project investigating social differences in healthy ageing.