Birth Weight and Weight Changes from Infancy to Early Childhood as Predictors of Body Mass Index in Adolescence.

OBJECTIVE: To assess the time point during infancy and early childhood at which greater than expected weight gain is associated with overweight in adolescence. STUDY DESIGN: Current height, weight, and body mass index (BMI) were assessed in 1520 adolescents (mean age of boys, 15.52 ± 0.84 years; mean age of girls, 15.37 ± 0.77 years). Information on weight and height trajectories during infancy and early childhood (birth and 6 other time points) was extracted from mother-child booklets. Conditional relative weights were computed to estimate greater or lower than expected weight gain (ie, soft tissue gain at a specific age independent of linear growth), and their association with BMI in adolescence was investigated using linear regression analysis. RESULTS: The mean BMI in adolescence was 21.77 ± 3.69 in boys and 21.70 ± 3.50 in girls. The proportion of overweight was 14.8% in each group. Overweight adolescents had significantly higher weight z-scores at birth, 1.2 month, 3.3 months, 7.6 months, 1 year, 2 years, and 4 years of age as compared with normal-weight adolescents. There were significant positive associations of weight z-scores and conditional relative weights with adolescent BMI at all ages except birth, which were strongest after the first year of life. In a majority of overweight adolescents, overweight had manifested within the first 4 years of life. CONCLUSIONS: Greater than expected weigh gain at any time in the first years of life is associated with an increased BMI in adolescence. The effect is strongest after the first year.

Six-minute walk distance in overweight children and adolescents: effects of a weight-reducing program.

OBJECTIVE: To assess the significance of consecutive six-minute walk tests (6MWTs) during a weight reduction program. STUDY DESIGN: Overweight children and adolescents (n = 113; mean ± standard deviation age, 12.9 ± 2.0 years; 64 girls) performed a standardized 6MWT at the beginning and end of an in-patient weight reduction program consisting of exercise, diet, and educational and psychological support. Their 6-minute walk distance (6MWD) was compared with age- and sex-matched normal-weight children (n = 353). RESULTS: Preintervention 6MWD averaged 93% of control subjects (631 ± 88 m versus 675 ± 70 m, P < .001) and increased significantly to 667 ± 90 m (P < .001) after 27 ± 7 days of intervention (99% of control subjects; P = .260). Participants reduced their body weight from 80.9 ± 19.8 kg to 75.6 ± 19.0 kg, body mass index (BMI) percentile from 98.2 ± 2.1% to 96.8 ± 3.8%, and BMI-standard deviation score from 2.37 ± 0.6 to 2.13 ± 0.6 (P < .001 for each variable). BMI-standard deviation score, height, and the change in heart rate during the 6MWT were significant independent predictors of the 6MWD at preintervention and at post intervention time points (P < .001 each). CONCLUSIONS: The 6MWD increases during a weight reduction program, indicating improvement of physical fitness and decreased metabolic demand during daily activities in overweight children. The 6MWT represents a practical and reliable assessment tool for exercise performance in overweight children and adolescents.

Six-minute walk test in children and adolescents.

OBJECTIVE: To evaluate the 6-minute walking distance (6MWD) for healthy Caucasian children and adolescents of a population-based sample from the age of 3 to 18 years. STUDY DESIGN: Two hundred and eighty boys and 248 girls completed a modified test, using a measuring wheel as incentive device. RESULTS: Median 6MWD increased from the age of 3 to 11 years in boys and girls alike and increased further with increasing age in boys (from 667.3 m to 727.6 m), whereas it essentially plateaued in girls (655.8 m to 660.9 m). After adjusting for age, height (P = .001 in boys and P < .001 in girls) remained independently correlated with the 6MWD. In the best fitting and most efficient linear and quadratic regression models, the variables age and height explained about 49% of the variability of the 6MWD in boys and 50% in girls. CONCLUSION: This modified 6-minute walk test (6MWT) proved to be safe, easy to perform, and highly acceptable to children. It provides a simple and inexpensive means to measure functional exercise capacity in children, even of young age, and might be of value when conducting comparable studies.