Six things we learnt from the latest childhood obesity data for England
www.nesta.org.uk/data-visualisation-and-interactive/six-things-we-learnt-from-the-latest-childhood-obesity-data-for-england/
www.nesta.org.uk/data-visualisation-and-interactive/six-things-we-learnt-from-the-latest-childhood-obesity-data-for-england/
Childhood obesity is a major problem. Earlier this year, UNICEF declared that worldwide more children are now obese than are underweight.
England is no exception. Today around one in ten children in reception are obese, according to the latest data from the National Child Measurement Programme (NCMP). For year 6, the rate is now over a fifth.
As well as causing various health complications for the children in question, childhood obesity is a key determinant of excess weight and ill health among adults. In fact, research shows that obese children and teenagers are about five times more likely to be obese when they grow up, and face a higher chance of premature death and disability in adulthood as a result.
The latest NCMP data also reveals a number of ongoing disparities in obesity prevalence. Children from Black ethnic groups are more likely to be obese, while those from South Asian ethnic groups have a higher chance of being underweight. At the same time, children living in the most deprived areas of England are twice as likely to be obese than those from the least deprived households. This ‘deprivation gap’ has widened over the past decade or so.
Many children are growing up in environments where the food that is most readily available is increasingly unhealthy. This is because of things like portion sizes and the nutritional value of meals in restaurants or takeaways, as well as the convenience of unhealthy foods in shops. The way food is promoted, advertised and displayed also plays a part, as does the fact that some parts of the country are flooded with fast-food shops, while places to buy fresh fruit and vegetables can be a bus ride away.
In the past, policymakers have focused on boosting children’s ‘healthy food literacy’ in schools to try to bring down childhood obesity. But research by Nesta shows that, when compared with preventive measures that target the wider food environment, such an approach is both costly and ineffective. For children, this is largely because they have almost no control over their food environment in the first place. Education without agency is a dead end.
Before we dive into the NCMP data, it is worth quickly setting out two points: how obesity and other BMI classes for children are measured; and how children put on weight slightly differently to adults.
Starting with measurement, BMI definitions for children are relative rather than absolute. For adults, each weight class is defined by a fixed BMI threshold. For example, someone is generally considered obese if they have a BMI of 30 or above (although there is some variation for different ethnic groups). Meanwhile, children’s weight classes are measured against a historical benchmark. In England researchers use the ‘UK90 growth data’– a survey of the height, weight, head circumference and BMI of 37,700 children in England, Scotland and Wales. The data serves as the ‘reference standard’ for assessing a child's BMI class.
Children are considered to be underweight if their BMI is equal to or below the 2nd percentile of the UK90 sample population (i.e. they are in the bottom 2% of the 1990 baseline by BMI). If they are between the 2nd and 85th percentile, they are considered to be a healthy weight. Anyone with a BMI between the 85th and 95th percentile is classed as overweight; those above the 95th percentile (i.e. the top 5%) are considered obese; and children with a BMI above the 99.6th percentile are said to be severely obese (a subset of obese).
Turning to physiology, research shows that children put on weight slightly differently to adults. When a child gains weight, their body increases its fat mass in two ways: hyperplasia and hypertrophy. Hyperplasia is where the body grows more adipocytes (or ‘fat cells’), while hypertrophy is where the body’s existing fat cells get larger, allowing them to hold more fat.
The body generally stops creating new adipocytes in adulthood, meaning the total number of cells ends up more-or-less fixed (although it can still vary slightly). When adults put on weight, their bodies generally rely on hypertrophy: their existing fat cells expand. But when children become overweight or obese, not only do they gain more adipocytes, but these cells also get ‘bigger’ (hyperplasia). This change in physiology can increase the chances of developing obesity later in life.
The NCMP is a mandatory yearly programme that measures the height and weight of state-school children in England at reception (aged 4-5) and year 6 (aged 10-11). Here are six things we learnt from the latest dataset.
1. The rate of obesity is creeping among reception and year 6 children, with the gap between year 6 boys and girls widening over the past 15 years
Obesity prevalence by sex, reception and year 6
For year 6 children, 22.2% are obese – a similar level to last year. The obesity prevalence gap between boys and girls aged 10-11 has also widened slightly since 2010, with boys more likely to be obese.
At reception, 10.5% of children are currently living with obesity. Boys are slightly more likely than girls to be in this BMI group, but – unlike in year 6 – the gap has narrowed slightly since 2007. For severe obesity at reception, prevalence has increased both for both boys and girls.
Across both age groups, there was a notable spike during the Covid-19 pandemic. Research suggests that the social isolation, online learning and the general decrease in physical activity caused by lockdown (in the UK and further afield) contributed to worsening obesity and metabolic health among children and young people. At the same time, there was also lower NCMP survey participation during the crisis, making the results harder to interpret accurately.
2. Obesity prevalence is highest in the North East of England for children in both reception and year 6
Obesity prevalence by UK region, reception and year 6
Obesity prevalence in both reception and year 6 varies by region. Starting with the younger group, across England the share of children aged 4-5 with obesity ranges across the country (9.4% in the East and South East versus 12.4% in the North East). For severe obesity, the North East and Yorkshire and The Humber have the highest prevalence (3.6%). The lowest figure rate is in the South West (2.4%).
In year 6, obesity prevalence also varies (19.2% in the South East versus 25% in the North East). For severe obesity, again the North East leads the pack (7.1%). The lowest shares are in the South East and South West (4.3%).
3. Obesity prevalence varies by London borough, with the gap between richer and poorer areas widening in year 6
Obesity by London borough, reception and year 6
Zooming in on London and obesity prevalence again varies. In reception, the share of children classified as obese ranges across the city – from 4.6% in Richmond to as high as 12% in Enfield. It’s a similar story for severe obesity (1.2% in Richmond compared with 4% in Newham).
By year 6, these disparities have widened. Across the board prevalence is much higher (from 12.1% in Richmond to 29.7% in Southwark). For severe obesity, rates also vary (2.6% in Richmond versus 8.5% in Southwark). For reference, Richmond has a substantially higher gross annual income per household than Southwark.
4. Children growing up in the most deprived households in England are much more likely to be obese or severely obese
Obesity by IMD, reception and year 6
If we divide the cohort of children into deciles using the Index of Multiple Deprivation (a measure of deprivation used to compare areas), a clear pattern emerges. Comparing the most deprived 10% of children (the 1st decile) with the least deprived 10% (10th decile) reveals a strong correlation between obesity and relative poverty.
Starting with obesity prevalence in reception, children living in the most deprived areas are twice as likely to be obese than those in the least deprived parts of England. For severe obesity the disparity is more extreme, with children in the most deprived areas three times more likely to be in this BMI group.
The gap widens in year 6. For children aged 10-11, children in the most deprived decile are twice as likely to be obese and four times as likely to be severely obese, when compared with children in the least deprived decile.
5. This deprivation gap is getting wider, particularly for children in year 6
Obesity prevalence for IMD 1 versus 10, reception and year 6
For children in reception, over the past 18 years obesity prevalence has increased for those living in households in the most deprived decile (from 11.9% in 2007/08 to 14% in 2024/25). Over the same period – but excluding during the pandemic – prevalence among children from the least deprived households has remained broadly level (at just under 7%). Overall, the ‘deprivation gap’ for children aged 4-5 with obesity has increased (from 5.1 to 7.1 percentage points).
For severe obesity prevalence among children in reception, the gap has also widened (again, ignoring the pandemic spike for now). In 2007/08 the difference between the least and most deprived areas was 2.3 percentage points. In 2024/25, this has stretched to 4.1 points.
Turning to year 6, the gap in obesity prevalence between the least and most deprived groups has increased even more dramatically (from 9.6 percentage points in 2007/08 to 15.8 points in 2004/25). Over the same period, the deprivation gap for severe obesity prevalence increased from 3.6 percentage points to 6.8 points.
6. Children from Black ethnic backgrounds are more likely to be obese, while South Asian children are the most likely to be underweight
BMI class by ethnic group, reception
BMI class by ethnic group, year 6
Obesity prevalence varies by ethnic group. According to the NCMP statistical report, some of these differences may be because of “factors such as area deprivation and physiological differences such as height”. Unlike adult BMI thresholds, which have been revised in recent years to recommend lower boundaries for overweight and obese classification for certain ethnic groups, children’s BMI measurements are based on the UK90 reference dataset and do not directly account for differences in ethnicity. These figures should be interpreted with caution, as a result.
Turning to the data, for children in reception obesity prevalence was highest among children from a Black African ethnic background, at 14.5%. In contrast, just 4.2% of children from a Chinese ethnic background were obese. At the other end of the scale, South Asian children – including from Indian, Bangladeshi and Pakistani backgrounds – were more likely to be underweight.
For children in year 6, the trend is similar. As of 2024/25, 31.4% of children from ‘any other Black background’ were obese, and 10.4% of those from a Black Caribbean ethnic group were severely obese. Children with Indian and Pakistani heritage were most likely to be underweight, at 5.2% and 4%, respectively.
The NCMP report only covers children in England. The way childhood obesity data is collected also varies across the rest of the UK. This makes it difficult to make direct comparisons. Even so, it is worth noting some of the common trends across the devolved nations.
For Wales, the latest dataset we have is the 2023/24 Child Measure Programme for Wales. As it stands, 13.7% of children in Wales are overweight and 11.8% are obese. Like in England, children living in the most deprived 20% of households in Wales are more likely to be living with overweight or obesity. There is also a slight rural-urban divide, with 26.8% of children in the countryside either overweight or obese compared with 25% in urban areas.
In Scotland, children are measured at ‘Primary 1’ (aged five). According to Public Health Scotland, 22.3% of children were at risk of being overweight or obese in 2023/24 (the latest data). Again, the socioeconomic pattern is clear: 14% of children living in the most deprived areas were at risk, compared with just 6.4% of those living in the least deprived areas. Children from Black ethnic backgrounds were the most likely to be overweight or obese, and, as with England, boys were slightly more at risk than girls.
According to the latest figures from Northern Ireland’s Health Intelligence Unit from 2023/24, 25.3% of children measured in Primary 1 were considered overweight or obese. Deprivation stats tell a familiar story: 24.7% of children living in the most deprived areas of Northern Ireland are classed as overweight or obese, compared with 17.8% of children from the least deprived areas.
The rising number of cases of children in the UK starting school already either overweight or obese points to gaps and inadequacies in the country’s food system. This is magnified by deprivation: household food insecurity during infancy and early childhood is associated with increased risk of obesity. Receiving good nutrition during the early years of childhood is essential for giving children the best start in life, and this includes minimising their risk of being overweight or obese in adulthood.
Indeed, research from The Netherlands suggests the first five years of a child’s life are key to preventing obesity in years to come. For every single unit increase in BMI at age six, the risk of being overweight or obese at age 18 more than doubles. But if a child originally with a higher BMI reaches a healthier weight before age six, they no longer face a heightened chance of developing obesity in their late teens. At the same time, if the child in question returns to a healthier BMI when they are six or older, their risk of excess weight later in life remains elevated. Early intervention is a critical ingredient for prevention.
Changing the country’s food environment is an effective way to lower population-level obesity, including for children. A recent study by the National Institute for Health and Care Research (NIHR) shows that children living in areas with more hot food takeaways are more likely to be obese. In fact, an extra takeaway per square kilometre is associated with a 0.05 percentage point increase in obesity prevalence among both reception and year 6 pupils, even after controlling for factors like ethnicity, deprivation and supermarket density. This suggests that altering the food environment – such as by restricting certain food outlets near schools – could help tackle childhood obesity.
Other preventative measures include the introduction of a healthy food standard for supermarkets – something included in the government’s 10 Year Health Plan. Around 80% of calories consumed come from supermarkets, so targeting this part of the food environment makes sense. And given that in most cases children cannot shape their own diets and tend to eat food purchased by adults, finding ways to make the weekly shop healthier could help bring down childhood obesity. Not only could this improve the health and wellbeing of children living with obesity today, helping tackle everything from obesity-related complications like type 2 diabetes to poor mental health and bullying, but it could also help lower adult obesity prevalence in generations to come.
The data tells a clear story. Childhood obesity in England is increasing, with serious consequences for those children both now and into their futures. But it doesn't have to be that way. Making progress now, with well-evidenced policy action, can make an enormous difference to the health and wellbeing of children in the UK.
