Children Grow More During the School Year Than Summer Vacation, Study Says

Get ready to update their fall wardrobe!

By: Amanda Mushro

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Photo by: Janis Christie

Janis Christie

We love seeing the pictures of kids on their first and last day of school. They all look a little older, a little wiser, and usually a lot taller. While their report cards show their growth in reading, writing, science and math, we also get to see their growth in inches. According to a new study, there’s a reason your kid’s pants were looking a little shorter towards the end of the school year. Turns out, it’s because kids grow faster during the school year than they do in the summer months.

Researchers from the study say that it has long been believed that kids put on more weight during their summer vacation than they do when they are in school. This could be because they are snacking more, have a less rigid schedule, and are less active in the summer.

To find out the reasons behind this weight gain, researchers looked at 350 students at 41 different schools. What they found was children’s height increased faster over the school year months than in the summer months. In fact, kids grew an average of .055 cm a month during the school year. When looking at height gain over the summer, there was a growth rate of -0.1 cm a month. While these numbers may not seem like a lot, for growing kids, it is. Plus, the decrease in growth over the summer months could explain the summer weight gain.

"Despite the pattern of height gain showing greater increase in height during the school year, children's height gain influenced BMIz more strongly during the summer holiday year than during the school year, with weight gain showing a constant increase during the school year," said co-author Dr. Debbe Thompson. "This differential seasonal impact of height and weight on BMIz lead to a healthier BMI status during the school year."

If a child grows faster during the school year, the higher BMI in the summer is the result of less growth and not extra weight gain. While it may not be the case for all kids, it could explain the BMI increase trend.

Researchers say they aren’t sure why children are growing at a faster rate during the school year. "It's possible that the demands of the school year alter children's exposure to the daily light-dark cycle, which may cause the seasonal pattern in height. Additional studies on children who receive year-round schooling might help to answer this question," said study co-author Dr. Craig A Johnston. "What is clear is that children at the greatest risk of becoming overweight and obese have a less pronounced seasonal impact of height gain on BMIz, indicating they would benefit from obesity prevention efforts throughout the year."

However, even if kids aren’t gaining too much weight in the summer, researchers say parents should still encourage their kids to be physically active in the summer months and make better food choices.

With nicer weather, kids can ride bikes, go for walks, or spend time on a playground. Plus, if they have a friend or a parent to join them, it’s a lot more fun for everyone!


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