Physical activity affects boys and girls differently, study finds


Girls don’t lose body fat by being more physically active. The plumpness of your body is also not related to your activity level. However, researchers from the Norwegian University of Science and Technology have found these links for boys.

Being physically active has significant health benefits. But physical activity affects boys and girls differently. New research has examined the relationship between body fat and physical activity in children.

“We investigated the relationship between objectively measured physical activity and the proportion of body fat in boys and girls,” says Silje Steinsbekk, a professor in the Department of Psychology at the Norwegian University of Science and Technology.

The researchers measured the participants’ body composition rather than their weight and height. Questions have been raised such as does increasing physical activity lead to a decrease in body fat percentage over time? Or is it perhaps the other way around, that people who gain more body fat over time become less physically active?

In their work, published in the scientific journal ‘International Journal of Obesity’, the researchers examined children every two years from 6 to 14 years old. They found that activity level affects the two sexes differently.

“In girls, we found no relationship between their physical activity and the amount of body fat. Increasing physical activity did not lead to a reduction in body fat in girls, and body fat had no effect on changes in their physical activity,” says former researcher and first author Tonje Zahl-Thanem.

But in the case of boys, it’s different. The amount of body fat influences your physical activity. “Increased body fat in boys led to decreased physical activity two years later, when they were 8, 10 and 12 years old,” says Zahl-Thanem.

With one exception, increased physical activity had no effect on changes in body fat. We found that boys who are more physically active at age 12 have a lower proportion of body fat at age 14. This was not the case in an earlier stage of development,” says Steinsbekk.

The study did not investigate the reasons for these differences, but the researchers note that larger bodies are heavier and require more effort when exercising, which could explain why men whose body fat increases become less active over time. But why doesn’t the same happen with girls?

“Here we can only speculate, but boys are generally more physically active than girls, so when boys reduce their activity levels, the physical impact is greater,” says Steinsbekk.

We also know that boys with large bodies are less satisfied with their bodies, and body dissatisfaction is associated with less physical activity in boys but not in girls.

“Boys’ physical activity is likely more competitively oriented than girls’, and higher body fat impairs success. Both conditions may help explain why increased body fat leads to lower activity. .” in boys, but not in girls,” adds Lars Wichstrom, co-author of the study.

“It could also be that girls are more likely to be physically active as their body fat levels increase because more attention is paid to girls’ bodies and appearance,” the authors add.

Body Fat Influences Sedentary Activity in Boys Researchers also looked at the relationship between inactivity or sedentary lifestyle and body fat. In the same way that they objectively measured physical activity, they also measured how long participants were sedentary during the day.

The results show that boys who had an increase in body fat percentage had a corresponding increase in sedentary activity two years later. This was maintained in all age groups studied, from 6 to 14 years. In other words, children whose proportion of body fat increases become more sedentary.

However, in the case of girls, no relationship was observed. Body fat percentage did not affect their level of inactivity over time, nor did they become less active as they gained more body fat.

“In short, we found a relationship between physical activity, sedentary lifestyle, and body fat percentage in boys, but not in girls,” Steinsbekk concludes.

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