[Association between timing for introducing complementary foods and body composition of children aged 3-5 years in five provinces of China].

OBJECTIVE: To explore the association between different timing of introducing complementary foods during infancy and the body composition of children aged 3-5 years. METHODS: The data was from National Nutrition and Health Systematic Survey for 0-18 Years Old Children in China. A face-to-face interview to caregivers of children was conducted to retrospectively collect timing of introducing complementary foods of children aged 3-5 years. The bioelectrical impedance analysis was used to measure the body composition of children by professionally trained investigators. The exposure variable of the study was the timing of introducing complementary foods(≤5 months old, 6 months old and ≥7 months old). The outcome variables were the fat-free mass, fat-free mass index, body fat mass, body fat mass index, and percentage of body fat. According to age stratification, a multivariate linear regression model was used to calculate the mean, mean difference and 95% CI after adjusting for potential confounders. RESULTS: After adjusting for potential confounders, there were no statistically significant difference in body fat mass, body fat mass index, percentage of body fat and fat-free mass index among different groups of timing for introducing complementary foods for children aged 3-5 years old. For children aged 3-5 years, after adjusting for potential confounders, the difference of fat free mass was statistically significant among children with different timing for introducing of complementary foods(3 years old: 12.89 kg vs. 12.66 kg vs. 12.94 kg, F=4.42, P=0.013; 5 years old: 16.27 kg vs. 16.23 kg vs. 16.66 kg, F=5.40, P=0.005). The fat free mass of children aged 3 years was lower when introducing complementary foods during 6 months of age than at ≤5 months of age(mean difference=-0.23 kg(95% CI-0.45--0.02 kg)). The fat free mass of children aged 5 years was higher when introducing complementary foods at ≥7 months of age than at≤5 months of age(mean difference=0.39 kg(95% CI 0.08-0.70 kg)). CONCLUSION: It is found that the association between timing for introducing complementary foods during infancy and the fat mass indicators of children aged 3 to 5 years was not statistically significant, and the association between timing for introducing complementary foods and fat-free mass may be inconsistent for different fat-free mass indicators.