Body Mass Index and Physical Activity of Elementary Minority Students

Purpose

The purpose of this study was to examine the relationship between body mass index (BMI) and physical activity (PA) and to see how BMI changes over time without intervention.

Methods

In total, 71 third to fifth grade students participated in the study; 33 males and 38 females. 76.1% (54) of the students were Latino and 23.9% (17) were African American. Height and weight measures were recorded five times over the course of a school year and BMI was calculated using a standard BMI formula. Students were classified as “healthy” (<85th %-tile), “at-risk” (85th - < 95th %-tile), or “overweight” (≥ 95th %-tile) according to BMI-for-age charts. Students wore a pedometer for seven consecutive days, four separate times throughout a semester. Daily PA was calculated by taking the mean number of steps per day.

Analysis/Results

Four-way ANOVA was used to test differences between gender, ethnicity, grade, and BMI classification in relationship to PA. Repeated measure ANOVA was employed to examine changes in BMI over time. More than half the population was above a healthy weight with 23.9% at-risk and 32.4% overweight. Results of the four-way ANOVA revealed a significant difference in PA between BMI classifications (p < .05) with healthy students averaging 396 more steps per day than overweight students. Boys took significantly more steps per day than girls at each BMI classification (p < .05) with the largest difference seen between overweight boys (M = 7191, SD = 2148) and overweight girls (M = 5469, SD = 1455). There were no significant differences in PA based on ethnicity or grade. BMI fluctuated throughout the school year with an average increase of ~1 BMI point between the first and last measurement (p < 0.001).

Conclusions

The percentage of students classified as overweight in this study (32.4%) was greater than the national average of 18.8% and much greater than the Healthy People 2010 goal of 5%. Differences in PA between BMI classifications and gender suggest that specifically targeted interventions may be necessary to increase PA and decrease BMI in each sub-population, especially overweight girls. BMI for the whole group appears to be continuing to increase over time without intervention. Therefore, this minority population may be ideal for an innovative PA and BMI intervention. A slowing of the BMI increase may even be considered a successful intervention effect in this group.