MONDAY, Nov. 21 (HealthDay News) -- The largest gains in body mass index (BMI) percentile are seen during elementary school, specifically between first and third grades, according to a study published online Nov. 21 in Pediatrics.
Ashlesha Datar, Ph.D., from the Pardee RAND Graduate School in Santa Monica, Calif., and colleagues investigated the critical periods of excess BMI gains by analyzing changes in BMI according to gender and race/ethnicity during elementary and middle school years. A nationally representative cohort of kindergarten students were followed during nine years, from 1998 to 2007. Height and weight measurements were collected for 4,240 white, 640 black, and 1,070 Hispanic children in kindergarten and first, third, fifth, and eighth grades. The proportion of children with BMI values in each quartile were estimated in each wave of the study. The time periods during which the largest gains in BMI percentiles occurred were estimated using piecewise linear growth models.
The investigators found that nearly 40 percent of children started kindergarten with a BMI in the top quartile of the growth charts. During the elementary school years, there was a significant increase in this proportion, with the largest gains (5.8 percent) seen between first and third grades. No further increase was seen during middle school. The most notable increases in BMI percentiles over time were found among Hispanic children and black girls.
"The early school years might be a critical time for excess BMI gains, even among children with normal BMI values at kindergarten entry," the authors write.
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