"Kids become dramatically less active over their years at primary school, study warns." This is the headline from The Sun reporting on a study of more than 2,000 children from primary schools in and around Bristol.
Physical activity is important for physical and mental health. UK recommendations are that children aged 5 to 18 should spend at least 1 hour a day doing moderate or vigorous activity. This is activity that would leave them breathing faster and feeling warmer, such as playground activities, walking briskly to school, dancing, cycling, playing football, and physical education at school.
In this study, the researchers used accelerometers (a wearable device that measures movement) to measure children's activity levels around age 6, 9 and 11. They found that all children became less active over time, with activity levels of girls and children who were overweight or obese dropping most.
Weekend activity levels fell more than weekdays, from an average 66 minutes of moderate activity a day at age 6, to an average of 53 minutes a day at age 11.
Taking account of weekend and weekday changes in activity, children lost an average of 63 minutes of moderate activity each week between age 5 and 11. Sedentary time – time spent not moving – increased.
With latest UK figures showing that around 23% of children aged 4 to 5 are overweight or obese, increasing to 34% of children who are age 11, the study supports the need to promote and maintain physical activity as children get older.
The researchers who carried out the study came from the University of Bristol and the University of Birmingham. The study was funded by the British Heart Foundation and published in the peer-reviewed International Journal of Obesity on an open access basis, so it is free to read online.
Mail Online got the figures for childhood activity wrong in its headline and the first sentence of its report, claiming "children do an hour less of exercise each day by the time they finish primary school". The figures show children do around 1 hour less each week, not each day. The Sun and BBC News gave more accurate, balanced reports.
This type of study is useful to look at trends over time, but it cannot tell us what is behind these trends.
Researchers recruited children in 57 schools in and around Bristol between January 2012 and July 2013. Children in year 1 (age 5 to 6) were measured and weighed, and wore activity monitors around the waist for 5 days, including 2 weekend days.
The process was repeated between March 2015 and July 2016 when children were in year 4 (age 8 to 9) and again between March 2017 to May 2018 when children were in year 6 (age 10 to 11).
The researchers collected data for 2,132 children in total, 512 of whom were included in all 3 phases of the study.
The children's weight and height were used to calculate their BMI and categorise them as being a healthy weight, overweight or obese. The researchers looked for links between BMI and activity levels. They also looked at whether the parents' education levels were linked to activity levels, and for differences between activity levels over time in girls and boys.
The researchers found that all children became less active and more sedentary over time. They calculated that moderate and vigorous activity levels decreased by 2.2 minutes per weekday each year, or 3.1 minutes per weekend day each year. That averaged to children spending 63 minutes less in moderate to vigorous physical activity each week at age 11 compared to at age 6.
The average amount of sedentary time (sitting or lying down) increased by 12.9 minutes per weekday each year. Girls were less active than boys at age 6, and that gap increased over time. At age 6, girls were doing 9.9 minutes less activity each day compared to boys. By age 11 the gap had increased to almost 15 minutes less activity each day.
At age 6, children who were overweight or obese were doing about the same amount of moderate or vigorous physical activity as children of a healthy weight. However, by age 11, children who had been obese at age 6, and remained obese, were on average doing 10 minutes less activity than children of the same age who were a healthy weight.
At the start of the study, 11% of children aged 6 were overweight and 8% were obese. By the end of the study, 14% of children aged 11 were overweight and 15% were obese. Most children (almost 8 in 10) who were overweight or obese at the start of the study remained overweight or obese at the end of the study.
The researchers said their findings suggest "a need to ensure that all groups of children are as active as possible so that there is less opportunity for differences in activity between groups to increase as children age".
They said that targeting "gender and BMI" would be the most effective ways to address differences in activity levels, to encourage girls and children who are overweight or obese to stay active.
This study adds to existing evidence that suggests children become less active as they get older. Previous studies have looked at the change between young children and adolescents, while this study shows the trend begins earlier, during the primary school years.
This seems to tie in with national figures that show between the start and end of primary school, the proportion of children who are overweight or obese increases. From 2018 to 2019, 22.6% of children in reception and 34.3% of children in year 6 were either overweight or obese.
The study also shows that children who are already overweight or obese at a young age are at greater risk of falling behind on physical activity as they get older. As healthy weight and overweight children are equally active at age 6, the study suggests that being overweight further increases the risk of inactivity.
Another interesting finding is that girls are less active than boys, and that this gap gets wider with age. It's not possible to know the reason for these observations, but the study supports the need to ensure that all children stay active throughout childhood – particularly girls, and overweight or obese children.
Keeping active during childhood means children's bones and muscles grow strong and reduces the chances of them developing long-term health conditions such as diabetes or heart disease in later life. Physical activity is also linked to better mental health.
It can be hard to ensure children get enough exercise, especially if they spend a lot of time playing online games or watching television. But building physical activity into their daily lives, such as walking or cycling to school and playing outdoors, can help.