Plenty of screen time during childhood, particularly during weekends, translates to higher body mass index (BMI) among young people. Folkhälsan’s recent study indicates that screen time tends to increase during the transition from childhood to adolescence.
Today’s children and young people grow up in front of displays. However, no one knows how much screen time is harmful or what the long-term physiological and psychological effects are that plenty of screen time involves. In co-operation with, among others, the University of Helsinki, the Fin-HIT researchers at Folkhälsan Research Center have monitored the screen time and weight development of more than 5,000 children over a period of three years. The average age of the children was 11 years at the beginning of the study and 14 at the end of the monitoring period. The results have been published in the esteemed scientific Journal of Adolescent Health.
– Not many longitudinal studies have been carried out in this field of research. The results of the existing studies have been highly conflicting, which has resulted in the inability to draw conclusions on causality, says researcher Elina Engberg at Folkhälsan Research Center.
The children themselves assessed how many hours of their free time they spent watching TV, videos and films on the one hand and how many with computers on the other—on school days and weekends alike. The children’s weight and height were measured at the beginning and end of the study. The increase of body mass index (BMI) among the 14-year-olds who spent plenty of time in front of the screen as children was higher than among those who reported lower screen times.
Most of us watch the screen while sitting still or in a lying position. When the body is still, energy consumption is lowered, which means screen time affects the body’s energy balance. This is why the correlation between high weight and screen time is no surprise to the research team. What was surprising was the rather strong connection between abundant screen time during weekends—at least four hours per day—and a future elevated BMI.
– During weekends, children have more time to spend watching the screen while they also have more time to move. Earlier studies had concentrated on the week as a whole. This is why the result was rather interesting, Engberg says.
Because more screen time during both weekdays and weekends translated to higher body mass index three years later, the researchers have concluded that high screen time increases the risk for higher BMI.
Apart from the weight increase, also screen time tends to get longer during the transition to adolescence. The proportion of children who spent at least three hours with TV or videos during weekdays grew from 16% to 23% during the surveyed three years. For those who watched TV or videos for at least four hours over the weekend, the increase was from 19% to 30%.
One way to prevent overweight among young people would be to replace the children’s passive screen time with more mobile activities. The Fin-HIT team advises independent sports hobbies and play as well as outdoor activities with the family combined with a healthy diet.
– It would be good if at least a portion of the screen time were to be exchanged for more active ways of spending time, such as being outdoors together—in essence, anything that results in a pause from the passiveness of the screen and gets the child to move, Engberg says.
Fin-HIT is a national scientific study of the health and lifestyle of children and young people. The purpose is to identify the impact of genes and lifestyle on the health of children today and in the future.
Postdoctoral researcher Elina Engberg, Folkhälsan Research Center and University of Helsinki, email@example.com, +358 40 566 2341
Adjunct professor, Fin-HIT team leader Heli Viljakainen, Folkhälsan Research Center and University of Helsinki, firstname.lastname@example.org, +358 50 448 5660