About this release

This release from Public Health Scotland provides annual statistics on high, low and healthy body mass index (BMI) for Primary 1 school children (those aged around 5 years old), and includes data for school years 2001/02 to 2020/21. Statistics in this release are derived from height and weight measurements collected at health reviews in Primary 1.

Main points

  • In school year 2020/21, 69.8% of Primary 1 children measured had a healthy weight, 29.5% were at risk of overweight or obesity and 0.8% were at risk of underweight.
  • There was a 6.8 percentage point increase in the overall proportion of Primary 1 children who are at risk of overweight or obesity between 2019/20 and 2020/21, having been stable for a number of years prior to this. The most substantial increase was in the proportion of children at risk of obesity.
  • Marked socioeconomic inequalities in child unhealthy weight have developed over the past 20 years. These have widened with the recent changes. Among children living in the most deprived areas there was an 8.4 percentage point increase between 2019/20 and 2020/21, to 35.7% at risk of overweight or obesity, compared to a 3.6 percentage point increase, to 20.8%, in the least deprived areas.
Image caption Percentage of P1 children at risk of overweight or obesity by deprivation level, 2001/02 to 2020/21
  • Boys in Primary 1 are slightly less likely than girls to have a healthy weight.
  • In school year 2020/21 approximately 37% of Primary 1 children were measured, compared to pre-pandemic review coverage of above 70%. However, the degree of change seen in results in 2020/21 cannot be accounted for solely by differences in the size and composition of the dataset.


Following closures due to Covid-19 in 2019/20, schools in Scotland reopened with restrictions in August 2020, before again closing to the majority of pupils during January to March 2021. This ongoing disruption meant that there was a reduced volume of data gathered through P1 reviews. In 2020/21, 21,024 children had valid height and weight measurements recorded, approximately 37% of P1 children. Further analysis has also been carried out to assess the comparability of this dataset, in terms of deprivation, geography, sex and age. Comparisons have been made with the 2018/19 dataset (the last year with relatively high coverage) and the 2020 population estimates. Although there are some differences in the composition of the data compared to earlier years, the scale and consistency of observed changes in 2020/21 suggest that there are true differences in the BMI distribution of P1 children.

A child's BMI is calculated by dividing their weight (in kilograms) by their height (in metres) squared. Children are then allocated to a healthy or unhealthy weight category by comparing their BMI to the range of BMIs seen among a reference group of children of the same age and sex. This summary provides information on the proportion of children found to be at risk of having an unhealthy weight based on the thresholds used for monitoring the health of the child population ('epidemiological thresholds'). The full report also provides information on the proportion of children found to have an unhealthy weight based on the stricter clinical thresholds used by health professionals caring for individual children. There is continued concern over the levels of overweight and obesity among children in Scotland. Obesity during childhood is a health concern in itself, and it can also lead to physical and mental health problems throughout adulthood. Being underweight in childhood can also be a cause for concern, indicating poor nutritional intake and/or underlying medical problems.

Further information

Public Health Scotland publishes a wide range of information on Child Health including infant feeding, immunisations, and early child development. Further information can be found in the Child Health section of the Data and Intelligence website.

The next release of this publication will be December 2022.

General enquiries

If you have an enquiry relating to this publication, please email phs.childhealthstats@phs.scot.

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Older versions of this publication

Versions of this publication released before 16 March 2020 may be found on the Data and Intelligence, Health Protection Scotland or Improving Health websites.

Last updated: 21 March 2024
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