Maintenance of lightweight correlates with decreased cardiovascular risk factors in early adolescence.

Purpose: To describe predictors of lightweight in 11-year-olds and how weight changes between ages 9-11 years affected selected cardiovascular risk factors.

Methods: Cohort study among an ethnically and geographically diverse group of 5098 nine-year-olds who participated in the Child and Adolescent Trial for Cardiovascular Health (CATCH) and were followed from 1991 to 1994 until age 11 years. Lightweight (body mass index [BMI] <15th percentile) was defined from gender- and age-adjusted data on the total population in the National Health and Nutrition Examination Survey I of 1971 to 1973. Weight (BMI) category at follow-up (age 11 years) was the dependent variable in the logistic regression. Gender, race/ethnicity, school site, weight category at baseline, and participation in the CATCH (intervention or control group) were examined for possible predictors.

Results: The prevalence of lightweight was much lower than the 15% expected at both ages 9 and 11 years; 4.7% for males (M) and 7.4% for females (F) and at age 11 years; 5.9% for M and 8.3% for F. Lightweight at age 9 years was the best predictor of lightweight at age 11 years (OR = 56.8; CI 41.3, 78.2). Normal-weight children who entered the overweight category exhibited striking adverse percent changes in serum cholesterol and in both serum high-density cholesterol and apolipoprotein B cholesterol levels. Among children in each weight group at age 9 years, the heavier children at age 11 years had higher percent changes in systolic blood pressure, and lower times on the 9-min run. Maintenance of lightweight was associated with the most favorable pattern of cardiovascular risk factors. Differences between groups were not found for percent change in total calorie intake or percentage of calories from fat. Normal-weight children who became overweight exhibited striking percentage increases in levels of serum cholesterol and in serum apolipoprotein B cholesterols.

Conclusions: Population-based anticipatory guidance about weight should focus on all children in mid-childhood, not only those at the upper extremes of weight. These who are genetically lean and healthy should be encouraged to remain so. Maintenance or achievement of lightweight was associated with favorable changes in systolic blood pressure in CATCH children during early adolescence. Those below the 5th percentile should be assessed and treated if eating disorders, undernutrition, or chronic illness are present. Optimal weight and optimal health should not be confused.