Gene-Breastfeeding Interaction on Body Mass Index Among Chinese Twins Aged 2-18 Years

The objective of this study was to investigate the gene-breastfeeding interaction on BMI based on the Chinese National Twin Register (CNTR). The study included 4,573 pairs of same-sex twins aged 2-18 from CNTR. Data were collected using a self-reported questionnaire, and a structural equation model was used to analyze the gene-environment interaction of breastfeeding with BMI in six age groups. Our findings indicate that as age increases, the heritability of BMI shows an increasing trend, being the lowest (h²: 0.08; 95% CI [0.00, 0.19]) in the 6- to 8-year age group and the highest (h²: 0.57, 95% CI [0.44, 0.72]) in the 12- to 14-year age group. Additionally, breastfeeding significantly modified the additive genetic component of BMI in the 6- to 8-year age group and 12- to 14-year age group. In the 6- to 8-year age group, breastfeeding decreased the impact of genes on BMI, with a genetic effect modification coefficient (βa) of -0.19 (-0.25, -0.13). In the 12- to 14-year age group, breastfeeding increased the impact of genes on BMI, with a genetic effect modification coefficient (βa) of 0.08 (0.02, 0.15). In conclusion, as age increases, the genetic influence on children's BMI becomes more pronounced. Breastfeeding may modulate genetic effects at the ages of 6-8 and 12-14. Given the metabolic diversity of obesity, our findings offer insight into how breastfeeding interacts with genetic background, helping to unravel the complex gene-environment interplay influencing obesity.