Long-Term Weight Trajectories in Infants Receiving Prolonged Breastfeeding: Impact of Formula Supplementation

Objective: This study compared weight trajectories in infants breastfed for at least 1 year, with or without formula supplementation. Study Design: A retrospective cohort of 252 infants followed in well-baby clinics. All infants were breastfed ≥12 months and received complementary foods at 4–6 months. Of these, 174 received no formula, and 78 received daily formula supplementation. Anthropometric data were collected from birth to 5 years of age. Results: Among males, those breastfed without formula had significantly lower body weight between 13 and 18 months compared with those receiving formula (10.20 kg vs. 10.97 kg, p < 0.001). From 19 months onward, no significant weight differences were observed and trajectories converged through 5 years. Conclusion: Prolonged breastfeeding in male infants is associated with lower weight in early toddlerhood; however, differences resolve by age two. These findings suggest early variations may represent physiological patterns. Further controlled studies are needed.