Background/Purpose
The goal of this study was to measure growth and fitness using field and laboratory measures in children over a school year to determine if normal weight and overweight children followed the same growth pattern and to examine fitness and activity patterns.
Method
Twenty-seven pairs of children matched on age, gender and ethnicity, ages 5-to-9 years were recruited from a sample of 115 children; one child in each pair was (at or above the 85th percentile for BMI and on was between 20th and 70th percentile. Anthropometric measurements, percent fat (Bod Pod); physical fitness (Fitnessgram and submaximal cycle ergometer) and physical activity (self-report) were measured at baseline and seven months later.
Analysis/Results
Six (20%) of the overweight participants were no longer overweight at the end of the study. A 2 x 2 (group by time) repeated measures Manova with seven growth indicators as dependent variables produced one significant interaction for mass, indicating that the overweight participants (OWG) gained more mass across time than the normal weight participants (NWG). The significant within subjects effects for growth (time) were stature, mass, lean body mass, subcutaneous fat and humerus breadth; consistent with normal growth expectations in children. Significant differences between groups were mass, lean body mass, subcutaneous fat, femur and humerus breadths, waist circumference and percent fat (Bod Pod). The OWG started the study larger and remained larger on all seven variables.
Using percent body fat (estimated from Bod Pod) to group participants into normal (below 20 and 30% for males and females respectively) and overweight (at or above 20 and 30% body fat) produced different classifications in 35% of the participants and agreement in 65% of the sample.
Moderate changes in fitness across time (mean effect size=0.5) and small group differences (es=0.2) for fitness variables were noted. For example, small to moderate differences were noted for the Pacer favoring the NWG at baseline (es=0.4) and end point (es=0.7). At baseline small differences favoring the OWG were found for total work output for the cycle ergometer (es=0.35) and exercise heart rate (es=0.43), however these group differences decreased at the end point.
Conclusions
Overweight and normal weight participants were more alike than different demonstrating similar growth patterns. The one exception was mass, the critical variable in determining overweight when calculating BMI. Physical activity parameters were similar at the end point, suggesting overweight children should not be viewed as more sedentary or less fit than normal weight children.