Title Page

Contents

Abstract 8

Ⅰ. Introduction 10

1. Importance of the timing of introduction of complementary food (CF) 10

2. Previous researches regarding timely introduction of CF 10

3. Purpose of this study 11

Ⅱ. Methods 12

1. Study Design and Setting 12

2. Participants 13

3. Exposures 14

4. Outcomes 15

5. Statistical Analysis 15

Ⅲ. Results 18

1. Patients 18

2. Early complementary feeding and body mass during childhood 21

3. Sensitivity and Subgroup Analyses 24

Ⅳ. Discussion 26

Ⅴ. Conclusions 29

Reference 30

국문요약 36

Table 1. Baseline demographic characteristics of children born in 2007-2008 who participated in the first round of the NHSPIC in South Korea 20

Table 2. Propensity score matched adjusted relative risk of overweight in children who were introduced to complementary food at 〈4 months of age vs ≥4 months 23

Table 3. Subgroup analysis for the risk of undesirable weight gain as defined by BMI z-scores. 25

Fig. 1. Study design. 12

Fig. 2. Flow Diagram of Cohort build. 19