Adolescence is a pivotal period: the habits acquired at this time tend to be perpetuated or even accentuated in adulthood, with the associated health effects. Unfortunately, the current context is particularly conducive to an increase in sedentary time, especially "screen time", with the development of a huge digital offering and new technologies that encourage even more sedentary behaviour. The effects of lockdown have further contributed to the trend towards physical inactivity and sedentary behaviour.
Using data from INCA3 (the third study on the food consumption and eating habits of the French population), ANSES decided to assess the health effects of young French people’s exposure to sedentary behaviour and low levels of physical activity. This expert appraisal follows on from the Agency's previous work, in particular its 2016 opinion on updating the guidelines for physical activity and sedentary behaviour, in which it had determined specific health thresholds for 6-17-year-olds associated with these two risk factors:
- sedentary behaviour: time spent sitting or lying down in front of a screen for recreation (television, computer, video game, etc.), outside school hours. When this screen time exceeds 2 hours per day, it can be a health risk;
- physical inactivity: when young people engage in less than 60 minutes per day of physical activity, including sport practised during school hours, they are considered to be insufficiently active.
Physical inactivity and sedentary behaviour: two thirds of 11-17-year-olds exceed both health thresholds
According to the expert appraisal conducted by the Agency, among young people aged 11 to 17 years:
- 66% face a worrying health risk, with both health thresholds being exceeded simultaneously: more than 2 hours of screen time and less than 60 minutes of physical activity per day;
- 49% present a very high health risk characterised by stricter thresholds, i.e. more than 4.5 hours of daily screen time and/or less than 20 minutes of daily physical activity. Of these, 17% are particularly exposed, with very high levels of sedentary behaviour (more than 4.5 hours of screen time per day) and physical inactivity (less than 20 minutes of exercise per day);
- the level of sedentary behaviour is even higher among older adolescents (15-17 years) and young people from underprivileged backgrounds.
Moreover, among 11-14-year-olds, fewer girls (15.5%) than boys (24%) engage in at least 60 minutes of physical activity per day.
The results of this expert appraisal are of great concern to ANSES. It is extremely rare for a risk assessment to show that two thirds of the studied population exceed the health thresholds, indicating exposure to a high health risk.
Inadequate physical activity: a health risk in its own right
ANSES points out that high levels of sedentary behaviour, i.e. long periods of screen time, are most often associated with risks of overweight and obesity in children, but also with eating disorders and impaired quality of sleep and life. Physical activity can however reduce the negative health effects of screen time. Besides sports, other forms of exercise such as walking, playing outdoor games, carrying loads or going up and down stairs also contribute to physical activity.
Physical activity has long been considered beneficial to health without being essential to it. ANSES now recommends that inadequate physical activity should, like sedentary behaviour, be considered as a health risk factor in its own right.
Promoting and strengthening physical activity from adolescence onwards: a major public health issue
As early as 2016, ANSES recommended interrupting sedentary time as regularly as possible (getting up, stretching, etc.) and reducing screen time by replacing it with periods of physical activity, including activity of low intensity and short duration.
In addition to these recommendations, ANSES is today alerting the public authorities to the need for reinforced measures on this subject in the framework of the National Nutrition & Health Plan (PNNS), and insisting on the importance of promoting measures to:
- combat sedentary behaviour among young people, particularly among older adolescents (15-17 years) and those in the most underprivileged categories;
- develop the physical activity of young teenage girls, in particular by raising awareness among children/adolescents, parents and educational personnel;
These measures will have to combine efforts to tackle both sedentary behaviour and physical inactivity, so as to reduce their prevalence among the profiles most at risk.
In general, the Agency reiterates that reducing the risks associated with sedentary behaviour and physical inactivity requires the creation of an overall environment conducive to behavioural change, both at an individual and collective level: at home, at school, in public spaces through the development of cycle paths, etc. In this sense, it stresses the importance of the measures taken by Santé publique France within the framework of the PNNS, which aim to foster the emergence of an environment conducive to an active lifestyle, improve the knowledge and skills of the public, and involve health, social and education professionals.
A reminder of ANSES’s 2016 recommendations:
- promote the practice of physical activity of different types (cardiorespiratory, muscle strengthening, flexibility) and identify all the opportunities for practice: moving around, carrying loads, going up or down stairs, being active in the home, etc. are all types of physical activity;
- encourage a reduction in sedentary behaviour, by decreasing the total time spent sitting on a daily basis and interrupting extended periods of inactivity with active breaks. The concomitance of an increase in physical activity and a reduction in accumulated continuous sedentary time will produce the greatest effects on health.