Official Statistics

NCMP changes in the prevalence of child obesity between 2019 to 2020 and 2020 to 2021

Published 27 April 2022

Applies to England

1. Main messages

• Prior to 2020 to 2021 prevalence of obesity and severe obesity has seen only small annual changes that have not exceeded 1.1 percentage points, since the start of the NCMP in 2006.
• In 2020 to 2021 unprecedented increases were seen in the prevalence of obesity of 4.7 percentage points in Reception boys, 4.4 percentage points in Reception girls, 5.6 percentage points in Year 6 boys and 3.3 percentage points in Year 6 girls.
• Boys, particularly in Year 6, have experienced the largest increases in obesity and severe obesity.
• These increases in child obesity and severe obesity prevalence in 2020 to 2021 follow the COVID-19 pandemic which resulted in school closures and other public health measures. More data is needed to know whether this is a long-term increase.
• The largest increases in the prevalence of obesity and severe obesity in boys and girls have occurred in the most deprived areas of England, resulting in the large and persistent disparities in child obesity having worsened.
• Disparities in obesity prevalence between ethnic groups have also increased with the ethnic groups that previously had the highest obesity prevalence, in the most part, experiencing the largest increases.

2. Introduction

This report examines the changes in the prevalence of obesity and severe obesity between academic years 2019 to 2020 and 2020 to 2021 using data from the National Child Measurement Programme (NCMP). This period covers data collected between September and March 2020 before the start of the COVID-19 pandemic (2019 to 2020 NCMP) and compares with data collected one year later between March and April 2021 (2020 to 2021 NCMP). It can therefore be used to help assess the wider impact of the pandemic, such as school closures and other public health measures, on the physical health of children.

The NCMP is an annual programme that in a normal year measures the height and weight of over 1 million children per year in Reception (aged 4 to 5 years) and Year 6 (aged 10 to 11 years) in mainstream state-funded schools in England. Although the NCMP only covers certain age groups, it normally includes most children in those year groups (usually around 95% of eligible children).

The NHS Digital NCMP 2020 to 2021 annual report showed large increases in the prevalence of obesity and severe obesity in 2020 to 2021. Similar increases in overweight and obesity prevalence were reported by Public Health Scotland in their child measurement report for 2020 to 2021. This report builds on those findings to identify which population groups in England experienced the largest and smallest increases in the prevalence of obesity and severe obesity and investigates whether existing disparities in child obesity have improved or worsened.

The 2020 to 2021 and 2019 to 2020 NCMP data collections were both impacted by the COVID-19 pandemic response; the 2019 to 2020 NCMP stopped in March 2020 when schools were required to close and the start of the 2020 to 2021 NCMP was delayed until March 2021.

For the 2020 to 2021 data collection, local authorities were asked to collect a nationally representative sample of data. Around 300,000 children (25% of previous full measurement years) were measured but the sample was not fully representative of the child population. Therefore, weighting was applied to the analysis to make it comparable to previous years of NCMP data.

In 2019 to 2020 the number of children measured (890,000 children) was around 75% of previous years. Analysis by NHS Digital and the Office for Health Improvement and Disparities (OHID) at the time showed that national level data was reliable and comparable to previous years for 2019 to 2020. Further information is available in the NHS Digital NCMP 2019 to 2020 annual report.

Though the data for 2019 to 2020 and 2020 to 2021 is comparable to previous years some caution should be exercised as fewer children were measured than usual. Additionally, it is not known whether the recent increase in child obesity, identified in the 2020 to 2021 NCMP, is evident across children of all ages and whether trends will continue at this new higher rate or begin to return to pre-pandemic levels.

3. Trends over time

The increase in obesity prevalence in 2020 to 2021 is the largest increase recorded in the NCMP since the programme began in 2006 to 2007. In previous years this report has looked at trends over time across all years of NCMP data. However, due to the unprecedented increase seen in prevalence of obesity in 2020 to 2021 compared to previous years, the usual method to assess change over time does not tell the whole picture. In this report we will focus on the recent increases in obesity and severe obesity prevalence and how they vary between different population groups.

Figure 1 shows how obesity prevalence has seen a sharp increase in 2020 to 2021 for children in Reception and Year 6:

• between 2019 to 2020 and 2020 to 2021 obesity prevalence increased 4.7 percentage points in Reception boys, 4.4 percentage points in Reception girls, 5.6 percentage points in Year 6 boys and 3.3 percentage points in Year 6 girls
• prior to 2020 to 2021 prevalence of obesity and severe obesity has seen only small annual changes that have not exceeded 1.1 percentage points, since the start of the NCMP in 2006

3.1 Figure 1: obesity prevalence by age and sex between 2006 to 2007 and 2020 to 2021

Low participation levels for Year 6 between 2006 to 2007 and 2008 to 2009 led to underestimation of obesity prevalence, represented by dotted lines on the chart.

Figure 2 clearly shows the increase in severe obesity prevalence in 2020 to 2021 for children in Reception and Year 6:

• between 2019 to 2020 and 2020 to 2021 severe obesity prevalence increased by 2.5 percentage points in Reception boys, 1.9 percentage points in Reception girls, 2.1 percentage points in Year 6 boys and 1.2 percentage points in Year 6 girls
• previous annual changes in obesity prevalence have not exceeded 0.4 percentage points, since the start of the NCMP in 2006
• the prevalence of severe obesity among boys in Reception has increased above the rate of severe obesity in Year 6 girls, where previously it had been consistently lower

3.2 Figure 2: severe obesity prevalence by age and sex between 2006 to 2007 and 2020 to 2021

Low participation levels for year 6 between 2006 to 2007 and 2008 to 2009 led to underestimation of obesity prevalence, represented by dotted lines on the chart.

4. Interpreting change charts presented throughout this report

This report uses charts to display the percentage point (pp) change in prevalence. An example to help interpretation is shown in Figure 3. The grey boxes show the change in prevalence of obesity (lighter grey), and severe obesity (darker grey) between academic years 2019 to 2020 and 2020 to 2021. The taller the box, the larger the change. The top of the box is the prevalence in 2020 to 2021 and the bottom of the box is the prevalence in 2019 to 2020. Throughout the report where an increase or decrease in prevalence is mentioned, it is statistically significant. Percentage point change values are not shown in the charts when the change is not significant. The spreadsheet published alongside this report also has a column to indicate which changes are statistically significant.

4.1 Figure 3: a guide to help interpret change charts

5. Changes in the prevalence of obesity and severe obesity by age and sex

Figure 4 shows the change in obesity and severe obesity prevalence by age group and sex. Important findings to note are:

• large increases in obesity and severe obesity prevalence in Reception and Year 6 for both boys and girls
• the increases in obesity and severe obesity for boys and girls in Reception were large particularly in relative terms; prevalence of severe obesity in boys nearly doubled between 2019 to 2020 and 2020 to 2021 from 2.7% to 5.2% (2.5pp)
• boys in Year 6 had a larger increase in obesity (5.6pp) and severe obesity (2.1pp) prevalence and from a higher starting point, compared with girls (3.3pp and 1.2pp respectively)

5.1 Figure 4: percentage point (pp) change in prevalence of obesity and severe obesity between 2019 to 2020 and 2020 to 2021 by age and sex

6. Changes in the prevalence of obesity and severe obesity by age, sex, and ethnic group

There are known disparities in weight status by ethnicity, with children from Black and some Asian ethnic groups having higher prevalence of obesity than children of White British ethnicity. Some of the differences in prevalence between ethnic groups could be due to confounding factors such as area level deprivation.

Figure 5a shows that between 2019 to 2020 and 2020 to 2021, for girls in Reception:

• the prevalence of obesity has increased for girls in all ethnic groups
• the prevalence of severe obesity has increased for White British, Indian, Pakistani, Black African, and Black Caribbean girls
• Black African girls, with the highest obesity prevalence had the largest increase in obesity prevalence (7.9pp), which is around twice that seen among White British girls (3.9pp)

6.1 Figure 5a: percentage point (pp) change in prevalence of obesity and severe obesity between 2019 to 2020 and 2020 to 2021 in Reception girls by ethnic group

In Reception boys between 2019 to 2020 and 2020 to 2021 (Figure 5b):

• prevalence of obesity has increased for boys in all ethnic groups
• prevalence of severe obesity increased for White British, Indian, Pakistani, Bangladeshi, and Black African boys
• Pakistani and Bangladeshi boys had the largest increase in obesity prevalence of 8.2 percentage points, this is a very large relative increase from 10.6% to 18.8% and 13.1% to 21.4% respectively
• White British and Black Caribbean boys had the smallest increase in obesity (4.0pp) and White British boys had the smallest increase in severe obesity prevalence (2.0pp)

6.2 Figure 5b: percentage point (pp) change in prevalence of obesity and severe obesity between 2019 to 2020 and 2020 to 2021 in Reception boys by ethnic group

In Year 6 girls between 2019 to 2020 and 2020 to 2021 (Figure 5c):

• prevalence of obesity has increased for White British, Indian, and Pakistani girls
• prevalence of severe obesity has increased for White British, Indian, Pakistani girls, Black African and Black Caribbean girls
• the largest increases in obesity prevalence were among Pakistani and Indian girls (5.7pp and 5.1pp respectively)

6.3 Figure 5c: percentage point (pp) change in prevalence of obesity and severe obesity between 2019 to 2020 and 2020 to 2021 in Year 6 girls by ethnic group

In Year 6 boys between 2019 to 2020 and 2020 to 2021 (Figure 5d):

• prevalence of obesity has increased for boys in all ethnic groups
• prevalence of severe obesity has increased for White British, Indian, Pakistani, Black African and Black Caribbean boys
• Black African boys experienced the largest increase in prevalence of both obesity (7.6pp) and severe obesity (3.5pp)

6.4 Figure 5d: percentage point (pp) change in prevalence of obesity and severe obesity between 2019 to 2020 and 2020 to 2021 in Year 6 boys by ethnic group

7. Changes in the prevalence of obesity and severe obesity by age, sex, and deprivation

There is a strong correlation between weight status and deprivation, with children living in the more deprived areas experiencing a higher prevalence of obesity. Data is presented using the 2019 Index of Multiple Deprivation (IMD), a measure of relative deprivation for small areas. The small areas are divided according to their deprivation rank into 10 equal groups (deciles), ranging from the most deprived (decile 1) to the least deprived (decile 10).

In Reception girls between 2019 to 2020 and 2020 to 2021 (Figure 6a):

• prevalence of obesity has increased in all deprivation groups
• prevalence of severe obesity has increased in all deprivation groups except decile 9 (the second least deprived decile)
• girls living in the most deprived decile have consistently had the highest rates of obesity and have now seen the largest increase in prevalence of both obesity and severe obesity
• obesity prevalence among girls living in the most deprived decile has increased by 7.3 percentage points from 13.0% to 20.2%, whereas prevalence in the least deprived decile increased by 1.8 percentage points from 5.8% to 7.5%

7.1 Figure 6a: percentage point (pp) change in prevalence of obesity and severe obesity between 2019 to 2020 and 2020 to 2021 in Reception girls by deprivation decile

In Reception boys between 2019 to 2020 and 2020 to 2021 (Figure 6b):

• prevalence of obesity and severe obesity has increased in all deprivation groups
• boys living in the most deprived decile have consistently had the highest rates of obesity and have now seen the largest increase in prevalence of both obesity and severe obesity
• obesity prevalence among boys living in the most deprived decile has increased by 6.7 percentage points from 13.5% to 20.3%, whereas prevalence in the least deprived decile increased by 1.9 percentage points from 6.2% to 8.1%

7.2 Figure 6b: percentage point (pp) change in prevalence of obesity and severe obesity between 2019 to 2020 and 2020 to 2021 in Reception boys by deprivation decile

In Year 6 girls between 2019 to 2020 and 2020 to 2021 (Figure 6c):

• prevalence of obesity has increased in all deprivation groups
• prevalence of severe obesity has increased for girls in deprivation deciles 1 to 6, and decile 8
• girls living in the more deprived deciles have consistently had the highest rates of obesity and now have seen the largest increases in prevalence of obesity and severe obesity
• obesity prevalence increased by 4.5 percentage points in the two most deprived deciles, compared with 1.8 percentage points in the least deprived decile

7.3 Figure 6c: percentage point (pp) change in prevalence of obesity and severe obesity between 2019 to 2020 and 2020 to 2021 in Year 6 girls by deprivation decile

In Year 6 boys between 2019 to 2020 and 2020 to 2021 (Figure 6d):

• prevalence of obesity has increased in all deprivation groups
• prevalence of severe obesity has increased in all but the least deprived decile
• boys living in the more deprived deciles have consistently had the highest rates of obesity and have now seen the largest increases in prevalence of obesity and severe obesity
• obesity prevalence increased by 8.0 percentage points in the two most deprived deciles, compared with 2.8 percentage points in the least deprived decile

7.4 Figure 6d: percentage point (pp) change in prevalence of obesity and severe obesity between 2019 to 2020 and 2020 to 2021 in Year 6 boys by deprivation decile

8. Changes in Slope Index of Inequality (SII) for obesity

The SII for obesity presented in this report measures how obesity prevalence varies by levels of deprivation, measured by the Index of Multiple Deprivation, of the population and summarises the level of disparities. Child obesity prevalence is calculated for each deprivation group (deciles representing approximately 10% of the population), then the SII is calculated based on these figures.

The SII takes account of health disparities across the whole range of deprivation within England and summarises this in a single number. The higher the value of the SII, the greater the disparity in obesity prevalence. Increasing SII over time indicates increasing disparities.

Figure 7 shows the trend in SII for obesity for boys and girls in Reception and Year 6. Important findings to note are:

• there was a large increase in disparities in obesity prevalence among both boys and girls in Reception and Year 6 in 2020 to 2021
• the SII was greater in Year 6 boys and girls than in Reception boys and girls; this indicates there were greater disparities in Year 6 than in Reception
• up to 2019 to 2020 the SII was increasing at a faster rate in Year 6 than in Reception, illustrated by the steeper gradient of the trend for Year 6
• in 2020 to 2021 Reception girls had the largest increase in the SII for obesity (5.9pp) followed by Year 6 boys (5.5pp)

8.1 Figure 7: trend in SII for obesity, by school year and sex

9. Changes in prevalence by weight category, age, sex, and rural urban classification

An area where a child lives is classified as either urban or rural based on the type of settlement in which residents in that area typically live. Areas are categorised using the 2011 rural / urban classification. In this report rural/urban classifications are grouped by settlement type: Urban, Town and Fringe, Village and Hamlet and Isolated Dwelling.

Between 2019 to 2020 and 2020 to 2021 (Figure 8a):

• in Reception girls, prevalence of obesity has increased in areas classified as Urban, Town and Fringe, and Village and severe obesity has increased in all categories
• in Reception boys, prevalence of obesity and severe obesity has increased in all categories
• in both boys and girls, the largest increases in prevalence of obesity (4.8pp and 5.0pp) and severe obesity (2.1pp and 2.7pp) were in urban areas

9.1 Figure 8a: percentage point (pp) change in prevalence of obesity and severe obesity between 2019 to 2020 and 2020 to 2021 in Reception children by rural/urban category

In Year 6 girls between 2019 to 2020 and 2020 to 2021 (Figure 8b):

• prevalence of obesity has increased in areas classified as Urban, and Town and Fringe, and Hamlet and Isolated Dwelling
• prevalence of severe obesity has increased for girls in areas classified as Urban, and Town and Fringe
• the largest increases in obesity and severe obesity were in girls living in urban areas (3.7pp and 1.4pp respectively)

In Year 6 boys between 2019 to 2020 and 2020 to 2021 (Figure 8b):

• prevalence of obesity has increased for boys in all categories
• prevalence of severe obesity has increased in areas classified as Urban, Town and Fringe, and Village
• the largest increases in obesity and severe obesity were in boys living in urban areas (6.1pp and 2.3pp)

9.2 Figure 8b: percentage point (pp) change in prevalence of obesity and severe obesity between 2019 to 2020 and 2020 to 2021 in Year 6 children by rural/urban category

10. Changes in the prevalence of obesity and severe obesity by age, sex, and region of child residence

In Reception girls between 2019 to 2020 and 2020 to 2021 (Figure 9a):

• prevalence of obesity and severe obesity has increased in all regions with some variation in the size of increase
• the largest increase in prevalence was in London (5.2pp) and the West Midlands (5.1pp)
• the smallest increases in prevalence were in the South West (obesity prevalence increased 2.5pp and severe obesity prevalence increased 1.1pp)

10.1 Figure 9a: percentage point (pp) change in prevalence of obesity and severe obesity between 2019 to 2020 and 2020 to 2021 in Reception girls by region of child residence

In Reception boys between 2019 to 2020 and 2020 to 2021 (Figure 9b):

• prevalence of obesity and severe obesity has increased in all regions with some variation in the size of increase
• the largest increase in obesity prevalence was in London (5.3pp), the East Midlands (5.2pp), the East of England (5.2pp), the South West (5.2pp), and Yorkshire and the Humber (5.1pp)

10.2 Figure 9b: percentage point (pp) change in prevalence of obesity and severe obesity between 2019 to 2020 and 2020 to 2021 in Reception boys by region of child residence

In Year 6 girls between 2019 to 2020 and 2020 to 2021 (Figure 9c):

• prevalence of obesity has increased in all regions with the largest increases seen in London (5.2pp) and North East (5.0pp)
• prevalence of severe obesity has increased in the North East, Yorkshire and The Humber, the East Midlands, the West Midlands, the East of England, London, the South East, and the South West

10.3 Figure 9c: percentage point (pp) change in prevalence of obesity and severe obesity between 2019 to 2020 and 2020 to 2021 in Year 6 girls by region of child residence

In Year 6 boys between 2019 to 2020 and 2020 to 2021 (Figure 9d):

• prevalence of obesity and severe obesity has increased in all regions with areas with the highest prevalence experiencing the largest increases
• as seen among girls the largest increases in prevalence of obesity and severe obesity were in boys living in London (7.3pp and 3.3pp) and the North East (6.8pp and 2.7pp)

10.4 Figure 9d: percentage point (pp) change in prevalence of obesity and severe obesity between 2019 to 2020 and 2020 to 2021 in Year 6 boys by region of child residence

11. Conclusion

Despite the delayed start in the 2020 to 2021 NCMP and consequently the smaller than usual number of children measured, analysis by NHS Digital and OHID demonstrate that the data is comparable to previous years. Some caution should still be exercised in terms of the exact size of the increases shown in this report as 2020 to 2021 is an incomplete year of data collection. However, detailed analysis of the data indicates that there has been an unprecedented increase in child obesity and severe obesity prevalence in 2020 to 2021 following the COVID-19 pandemic which led to school closures and other public health measures. More data is needed to know whether this is a long-term increase.

This report shows unprecedented increases in the prevalence of obesity of 4.7 percentage points in Reception boys, 4.4 percentage points in Reception girls, 5.6 in Year 6 boys and 3.3 in Year 6 girls. Prior to 2020 to 2021 prevalence of obesity and severe obesity has seen only small annual changes that have not exceeded 1.1 percentage points, since the start of the NCMP in 2006. Boys and girls in Reception have seen the largest relative increase in prevalence rates.

In both Reception and Year 6, boys had higher prevalence rates of obesity and severe obesity compared with girls in 2019 to 2020, and in 2020 to 2021 have experienced larger increases in obesity and severe obesity compared with girls. This is most apparent in Year 6 where obesity prevalence has risen from 23.6% to 29.2% in boys compared to 18.4% to 21.7% in girls.

Furthermore, the largest increases in the prevalence of obesity and severe obesity in boys and girls have occurred in the most deprived areas of England. It is children living in these areas that have previously, and continue to have, experienced prevalence that is at least double that of children living in the least deprived areas. This has resulted in the large and persistent disparities in child obesity having greatly worsened.

Disparities in obesity prevalence between ethnic groups have also increased with the ethnic groups that previously had the highest obesity prevalence, in the most part, experiencing the largest increases. Similarly, urban areas in England with the highest prevalence historically saw the largest increases in obesity and severe obesity prevalence in 2020 to 2021.

12. Methods and further information

12.1 2020 to 2021 data collection and weighting

The start of the 2020 to 2021 data collection was delayed until March 2021. Local authorities were asked to use the remainder of the academic year, from March to July 2021, to collect a nationally representative sample of data because it was not feasible to expect a full NCMP collection so late into the academic year. The sample collected was not fully representative of the child population. Therefore, weighting was applied to the analysis to adjust for under or over representation of demographic and socioeconomic groups and make it comparable to previous years of NCMP data. More information about the weighting of data is available in the methodology and data quality chapter of the NHS Digital NCMP 2020 to 2021 annual report.

12.2 Determining significant differences

Significance tests have been used in this report to determine whether differences between prevalence estimates are statistically significant.

When the confidence intervals do not overlap the differences are considered as statistically significantly different. However, in some cases, estimates with overlapping confidence intervals will still be statistically significantly different. Where confidence intervals overlap additional significance testing has been applied using the approach applied by NHS Digital in the annual NCMP report, the method is outlined in Annex F of the NHS Digital report appendices (PDF, 392KB).

12.3 Confidence intervals

A confidence interval is a range of values that is used to quantify the imprecision in the estimate of a particular indicator. Specifically, it quantifies the imprecision that results from random variation in the measurement of the indicator. A wider confidence interval shows that the indicator value presented is likely to be a less precise estimate of the true underlying value. Statistical significance was determined by non-overlapping confidence intervals.

Confidence intervals were calculated using the Wilson Score method which gives very accurate approximate confidence intervals for proportions and odds based on the assumption of a Binomial distribution. It can be used with any data values, even when the denominator is very small and, unlike some methods, it does not fail to give an interval when the numerator count, and therefore the proportion, is zero. The Wilson Score method is the preferred method for calculating confidence intervals for proportions and odds. The method is described in detail in APHO Technical Briefing 3: Commonly used public health statistics and their confidence intervals (PDF, 571KB).

12.4 Body mass index (BMI) classification definitions for population monitoring

Assessing the BMI of children is more complicated than for adults because a child’s BMI changes as they mature. Growth patterns differ between boys and girls, so both the age and sex of a child needs to be considered when estimating whether BMI is too high or too low.

In England the British 1990 growth reference (UK90) for BMI is recommended for use to determine weight status according to a child’s age and sex. Each child’s BMI is calculated and compared with the BMI distribution for children of their age and sex from the UK90 growth reference. For population monitoring purposes BMI is classified according to the following list using the UK90 growth reference:

• obesity: greater than or equal to 95th centile
• severe obesity: greater than or equal to 99.6th centile

Responsible statisticians, product lead: Caroline Hancock, Catherine Bray For queries relating to this document, please contact: [email protected]