The Health Behaviour in School-aged Children (HBSC) survey is a WHO collaborative cross-national study that monitors the health behaviours, health outcomes and social environments of boys and girls aged 11, 13 and 15 years every four years. HBSC has collected international data on adolescent health, including eating behaviours, physical activity, sedentary behaviour and, more recently, overweight and obesity, for over 25 years, allowing prevalence to be compared across countries and over time. This report presents the latest trends in obesity, eating behaviours, physical activity and sedentary behaviour from the HBSC study and highlights gender and socioeconomic inequalities across the WHO European Region.
Childhood obesity is considered one of the most serious public health challenges of the 21st century. Globally, around one in 10 young people aged 5–17 years are overweight or obese, with levels increasing rapidly in many countries and regions in recent years.
The primary causes of overweight and obesity can be traced to energy-related behaviours – physical activity, sedentary behaviour, eating behaviour and sleep – which contribute to an energy imbalance between calorie intake and energy expenditure. A recent report from the WHO Commission on Ending Childhood Obesity (12) identifies obesogenic environments as the key driver for low levels of physical activity and high levels of sedentary behaviour and intake of energy-dense foods. Obesogenic environments are characterized by physical and social–environmental features that encourage a sedentary lifestyle and offer ready availability of energy-dense, nutrient-poor food (12).
Physical activity levels are generally very low in young people in all countries and are lower among girls. Time spent being physically active declines through adolescence. Physical activity is a key determinant of energy expenditure, as it has a fundamental positive influence on energy balance and weight control. Regular physical activity in children and adolescents is important for obesity prevention (18,19) and supporting obese adolescents to manage their weight (20). Current global recommendations state that young people aged 5–17 years should accumulate at least 60 minutes of moderate-intensity physical activity every day and include vigorous-intensity activities at least three times a week. Physical activity includes play, games, sports, transportation, housework, recreation, physical education and structured exercise and may be undertaken in the context of family, school or community activities (21).
While modern life has reduced energy expenditure through physical activity to a minimum, sedentary behaviours dominate adolescents’ daily lives (22). Young people spend approximately 60% of their waking time sitting, which makes sedentary behaviour the most common behaviour (besides sleep) in children and adolescents (23). The steepest increase in sedentary behaviour occurs around 11 to 13 years, during the onset of puberty (15,24). Increasing evidence from observational studies indicates that sedentary behaviour is associated with a wide range of negative physical, psychological and socioemotional health outcomes, although findings from some prospective studies are less consistent (25,26). The level of evidence varies with the type of sedentary behaviour, with the most consistent findings being found for screen-based activities (25,26). Screen time is also associated with acute eating behaviours such as snacking, but this is not sufficient to explain the detrimental associations between screen time and cardiometabolic health and obesity (27). From a health perspective, it is important to recognize that sedentary behaviour and physical activity occur relatively independently of each other, and various combinations of high or low sedentary behaviour and low or high physical activity levels exist (28,29).
It is essential to develop effective strategies to reverse recent trends. The early years and important life transitions such as adolescence provide key opportunities to reinforce healthy behaviours that will also reap dividends later in life (30).