A study found that children’s height and weight vary with the seasons.
- A study found that children grow faster during the school year than during vacations and are more likely to be overweight in the summer.
- Children’s growth is seasonal with a peak in the spring and a trough in the fall.
- Different reasons can explain this seasonality phenomenon, including the demands of the school year.
It’s true: in Western countries, children can more easily be overweight or obese during the summer, partly due to changes in physical activity and diet.
A study dating from 2022 and published in Frontiers in Physiology could explain this phenomenon: children grow faster during the school year than during the summer.
Since body mass index (BMI) is the ratio of weight to height, faster vertical growth during the school year may lead to an increase in BMI in the summer.
A study of children entering kindergarten
Researchers followed 3,588 children entering kindergarten in September 2005 at one of 41 schools in the Fort Bend Independent School District, surrounding the town of Sugar Land, Texas. The fastest growth rate actually occurs during early childhood.
They followed the children, initially aged five or six, for five years. The height and weight of each child was measured twice a year, mid-September and mid-April.
A difference in seasonal growth
The researchers noted that vertical growth was seasonal: children grew faster during the school year than in the summer, with an average growth rate difference of 0.055 cm per month.
Interestingly, the linear growth graphs show a see-saw pattern, with peaks in the spring and troughs in the fall.
There was no difference in the rate of weight gain between seasons, but the combined height and weight data meant that BMI was highest in summer, hence the likelihood of being overweight or obese increased each summer.
Changes related to the school year
The reason for the seasonality of vertical growth is not clearly defined. “It is possible that the demands of the school year are changing children’s exposure to the daily light-dark cycle, which could be driving the seasonal height trend” explained study author Dr. Craig A Johnston, an associate professor in the Department of Health and Human Performance at the University of Houston.
Furthermore, accelerated growth and weight gain in children can be affected by temperature or humidity, and depending on Australian study published in 2017, stress can also affect children’s height.
Stress actually has a major role on the hormones responsible for growth. These hormones are particularly activated when we sleep. Good sleep is therefore particularly important for the normal growth of children.
The results of the 2022 study provide more information about the mechanisms that regulate children’s growth and the timing of weight gain. It could help prevent accelerated weight gain during the summer.
