Breastfeeding at 6 months of age had a positive impact on overweight and obesity in Japanese adolescents at 15 years of age

Aim A number of studies have indicated the potential benefits that breastfeeding has on reducing childhood obesity, but few studies have evaluated the effect on adolescent obesity. We examined the association between breastfeeding and overweight or obesity at 15 years of age using data from a large nationwide longitudinal study launched by the Japanese Government in 2001. Methods We analysed data for 26 164 participants with known infant feeding practices at 6 months of age, namely the duration of breastfeeding or formula feeding. Overweight or obesity at 15 years of age were calculated based on the subject's self‐reported height and weight. Multinomial logistic regression analysis adjusted the data for child factors, namely sex, siblings, birth weight and physical activity clubs and the maternal factors of age, educational attainment and smoking status. Results Formula feeding was associated with an increased risk of overweight or obesity at 15 years of age. The adjusted odds ratios (95% confidence intervals) were 0.99 (0.89–1.09) for partial breastfeeding and 1.23 (1.02–1.48) for formula feeding, when exclusive breastfeeding was the reference category. Conclusion Breastfeeding during infancy had potential benefits for overweight or obesity among 15‐year‐old adolescents. Our results provide further evidence of the importance of breastfeeding.