Childhood weight and height data from the last 65 years shows that youngsters born after the Second World War exhibited the opposite physical traits, with underprivileged children being shorter and lighter than their larger, socially-higher counterparts.
Over time, this disparity has reversed so that lower socio-economic groups are now heavier.
The paper, Socioeconomic inequalities in children’s weight reversed in the UK between 1953 and 2015, has been published in The Lancet Public Health journal.
Co-author Dr Will Johnson, of Loughborough University, said: “In this new paper, we brought in measures of socio-economic position to investigate how inequalities in childhood weight, height, and BMI have changed between 1953 and 2015.
“It used to be that lower socio-economic groups were shorter and weighed less, on average, than higher socio-economic groups.
“But over the last six decades, the inequality in childhood height has narrowed, which is a good thing, but the inequality in childhood weight has reversed, such that lower socio-economic groups are now heavier and have increased risk of obesity.”
The authors say that these trends highlight the powerful influence that the obesogenic environment has had on socioeconomically disadvantaged children, and the failure of decades of previous policies to prevent obesity and related socioeconomic inequalities.
Lead author Dr David Bann, from University College London (UCL), said: “Our findings illustrate a need for new effective policies to reduce obesity and its socioeconomic inequality in children in the UK – previous policies have not been adequate, and existing policies are unlikely to be either.
“Without effective interventions, childhood BMI inequalities are likely to widen further throughout adulthood, leading to decades of adverse health and economic consequences.”
The study included data for children born in England, Scotland and Wales from four longitudinal birth cohort studies beginning in 1946, 1958, 1970 and 2001.
Some 22,500 children were assessed at the age of seven years old, 34,873 were assessed at age 11, and 26,128 were assessed at age 15.
At the ages of seven, 11 and 15 years old, the children’s height and weight were measured, and BMI was calculated.
The father’s occupation was used as a marker of each child’s socioeconomic position, and the association between socioeconomic position and weight gain from childhood to adolescence was also analysed.