If overweight, your child will be less active

Over time, children with a higher fat mass reduce their level of physical activity and increasingly pursue sedentary activities such as watching TV or computer gaming.

Conversely, low levels of physical activity or too much time in front of the TV or computer do not cause normal-weighted children to put on weight.

The findings stem from a large study that has just been published in the journal, the International Journey of Obesity.

New knowledge about the linkage between physical activity and overweight children

The study presents an entirely new body of knowledge about the links between physical activity and being overweight because it investigates developments among test participants over time.

In contrast, most other studies have measured activity at a single point in time, making it impossible to establish whether activity levels affect being overweight, or whether being overweight influences the level of activity:

"The defining characteristic of our work is that we have left a period of six months in between our measurements of activity and weight. Thus, we have been able to investigate how an overweight child's level of activity develops over a half-year," says Mads Fiil Hjorth, a researcher of physical activity, sleep and obesity at the University of Copenhagen's OPUS Research Centre.

Mads Fiil Hjorth emphasizes that physical activity is of great value to children. "Even though our study, in part, shows that a lack of physical activity and lots of TV and computer do not cause children to gain weight, physical activity is obviously very good for children's general health and welfare in a number of other ways. We have not focused on these areas in this study. Instead, we have specifically focused on the link between physical activity and fat mass."

Danger not limited to those who are overweight

Associate Professor Anders Sjödin, head of OPUS' research into children's activity patterns, points out that the problem also extends to a segment of normal-weight children:

"It wasn't only those children who are classically understood as being overweight who demonstrated poor development in activity levels. There were also normal-weight children with slightly larger fat masses," according to Sjödin. "So, there is no doubt that if someone has a child with a bit too much to pinch around the midsection, parents need to stay attuned to the child's level of activity."

The Method

The study included 600 third and fourth grade children who were equipped with an activity tracker on two occasions, for seven days at a time. The activity tracker was worn at the start of the project and again after six months. The tracker was able to register around the clock activity levels.

These measurements were compared with measurements of fat mass at both the beginning and end of the project. Among other things, this demonstrated that children with the highest fat mass experienced the greatest reduction in the amount of activity over the half-year period.