Association of number of siblings, birth order, and thinness in 3- to 12-year-old children: A population-based cross-sectional study in Shanghai, China

Sibship size and structure have a significant association with overweight and obesity in children, but the relationship with thinness has not been fully studied and understood, especially in Asia. This study evaluated the associations among number of siblings, birth order, and childhood thinness and investigated the association of number of younger or older siblings with childhood thinness.