Title Page

Contents

Abstract 8

Ⅰ. Introduction 10

1. Background 10

Ⅱ. Materials and Methods 11

1. Study Population 11

2. Measurements 12

3. Statistical Analysis 16

Ⅲ. Results 17

1. Characteristics of study population 17

2. Age-related changes in TBLH BMD, Total-Body LM, and Total-Body FM 18

3. Crude Relationship between obesity parameters and TBLH BMD 22

4. Linear Relationship between Obesity Parameters and TBLH BMD 22

5. Non-linear Relationship between obesity parameters and TBLH BMD 23

Ⅳ. Discussion 26

Ⅴ. Conclusions 29

Appendices 30

References 30

Abstract(Kor) 34

Table 1. Numbers of people (aged over 5 years) and percentage of the population with overweight or obesity(using the WHO classification of +1SD and +2SD above median growth reference) ; body mass index(BMI) 10

Table 2. Sample distribution according to age groups, overall and by gender in 2060 Korean adolescents aged 10 to 19 years from the KNHANES 2008-2011. KNHANES: Korea National Health and Nutrition Examination Survey 11

Table 3. Gender- and age-specific 5th, 85th, and 95th percentiles of body mass index (BMI) based on the 2007 Korea National Growth Chart 15

Table 4. Sample distribution of gender-and-age-specific percentile groups of body mass index (BMI) by gender and age based on the 2007 Korea National Growth Chart 15

Table 5. Sample distribution of gender-specific percentile groups of waist circumference (WC), waist-to-height ratio (WHtR), and total-body fat mass (FM) by gender. WC: waist circumference; WHtR: waist-to-height ratio; FM: fat mass. * The percentile groups... 16

Table 6. Sample distribution according to age groups, overall and by menarcheal status 16

Table 7. Characteristics of study population by gender in 2060 Korean adolescents aged 10 to 19 years from the KNHANES 2008-2011. KNHANES: Korea National Health and Nutrition Examination Survey; SD: standard... 18

Table 8. Mean comparison between male and female by age group. CI: confidence interval; TBLH: total-body-less-head; BMD: bone mineral density; TB: total-body. *Statistical significances were assessed using t-test for two independent samples 20

Table 9. Multiple regression results using total-body-less-head (TBLH) bone mineral density (BMD) as the dependent variable by gender in 2060 Korean adolescents aged 10 to 19 years from the KNHANES 2008-2011. KNHANES: Korea National Health and Nutrition... 23

Table10. Multiple regression results representing curvilinear effects with the obesity variable squared (X²) as an independent variable by gender in 2060 Korean adolescents aged 10 to 19 years from the KNHANES 2008-... 24

Figure 1. DEXA Scan Results Image 13

Figure 2. Human body composition 14

Figure 3. Age-related changes in total-body-less-head (TBLH) bone mineral density (BMD), total-body lean mass (LM), and total-body fat mass(FM) by gender in 2060 Korean adolescents aged 10 to 19 years from the... 19

Figure 4. Unadjusted relationships between obesity and total-body-less-head(TBLH) bone mineral density (BMD) by gender in 2060 Korean adolescents 10 to 19 years from the Korea National Health and Nutrition... 21

Figure 5. Quadratic relationships between obesity and total-body-less-head bone mineral density (TBLH BMD) adjusted for age, menarcheal status (for females only), and total-body lean mass by... 26