For decades, children from poorer backgrounds have tended to be thinner than their wealthier peers.
But the rise of cheap junk food and lack of exercise by youngsters today has turned this trend on its head, a study has found.
Socioeconomic inequalities in children’s weight have reversed in the UK since WWII, according to data from between 1946 and 2016.
Researchers from University College London looked at how both the height and weight of children and teenagers have changed over the course of 70 years.
They found while poorer children have narrowed the gap in height thanks to the availability and affordability of food, unhealthier lifestyles have also seen their BMIs increase.
The University College London study found poor children born most recently weighed 4.6 lb (2.1 kg) more than those who are better off (file photo)
A third of children are overweight or obese at 11 in the UK, and the rates are creeping up despite Government promises to reduce them.
But without drastic action to curb sugar and fat content in food, the widening gap will only get worse, the researchers warn.
The study tracked more than 56,000 children born in England, Scotland and Wales in 1946, 1958, 1970 and 2001.
Researchers used height and weight measurements to calculate the child’s BMI at the age of seven, 11 and 15, while using the father’s occupation as a marker of the child’s socioeconomic position.
Between 1953 to 2015, the difference in children’s BMI levels between the most and the least disadvantaged children has expanded.
They found on average, those born in 2001 were taller, heavier and have a higher BMI than those born in the preceding decades.
Researchers found that across all year groups, the most disadvantaged children tended to be shorter. But this distance narrowed over time in seven-year-olds, from an average of 3.9cm in 1946 to just 1.2cm in 2001.
At the same time, differences in weight reversed.
While youngsters from poorer backgrounds were traditionally always lighter, those born most recently were heavier for the first time.
IS THERE A GROWING CHILDHOOD OBESITY PROBLEM IN ENGLAND?
Nearly half of primary school children are dangerously overweight in some parts of the country, according to official figures released in January.
Public Health England mapped the waistlines of 10 and 11 year olds using data from local authorities for the first time. The figures revealed that there is one ‘severely obese’ child for every classroom in the country.
The data showed a clear link between obesity and social deprivation – with the best and worst areas in the country being just five miles apart. Some 44 per cent of 11 year olds in the north London borough of Brent are either overweight or obese – the worst region in England. The figure is almost double that of the slimmest borough (25 per cent), Richmond-upon-Thames.
Paediatricians warned the map is evidence that successive Governments have failed to tackle childhood obesity, fueling ‘appalling life-long consequences’.
Rather than poorer children being 2kg (4.4lbs) lighter in the post war years, the equivalent 11-year-olds born most recently weighed 2.1kg (4.6lbs) more, compared to those who were better off.
This increased with age and meant the most disadvantaged 15-year-olds, now have a BMI score that is 1.4 higher than their richer peers, where none existed half a century ago.
Lead author Dr David Bann blamed the considerable changes to diets and physical activity levels in Britain since the post-war years, adding that the study showed previous policies to reduce obesity have not worked.
‘Without effective interventions, childhood BMI inequalities are likely to widen further throughout adulthood, leading to decades of adverse health and economic consequences,’ he said.
‘Bold action is needed, such as creating further incentives for food manufacturers to reduce sugar and fat content in food and drinks, reduce the advertising of unhealthy foods to children and families, and incentivise the sale of healthier alternatives.’
Tam Fry, from the National Obesity Forum, said it showed the least advantaged were generally adopting the least healthy lifestyles.
‘Though all children have grown in stature in the decades since the war, the end of rationing and simply more food enabled the poorest substantially to catch up in height,’ he said.
‘The downside, however, is that their staple diet has become progressively worse in comparison with that of richer families and in an obesogenic society its density has stayed with them.
‘The researchers are quite correct to call for a sea change in our food composition if further obesity is to be avoided in deprived areas.’
The research was published in The Lancet Public Health journal.