High serum leptin levels in infancy can potentially predict obesity in childhood, especially in formula-fed infants

AIM: To investigate serum leptin levels in breast-fed and formula-fed infants in infancy and their possible relationship to body mass index (BMI) in childhood. METHODS: We enrolled 237 healthy term infants between September 2000 and April 2004 and tested their serum leptin levels, took anthropometric measurements and calculated BMI. A follow-up study was carried out to evaluate the BMI of 89 of these infants in childhood, in relation to their serum leptin levels in infancy, at a median (interquartile range) age of 8.8 years (7.8-10.2). The statistical significance of this multivariate analysis was set at p < 0.05. RESULTS: Breast-fed infants had significantly higher serum leptin levels than formula-fed ones (p < 0.05). Children who were formula-fed in infancy had a significantly higher BMI, at follow-up, than those who were breast-fed (p < 0.001). Furthermore, we identified a leptin cut-off value of 2.7 ng/mL, below which infants had a higher BMI in childhood. CONCLUSION: A higher leptin level in infancy may be inversely associated with BMI in childhood, suggesting that this hormone in infancy is a potential predictor of obesity in later life. Further investigation is required to be conclusive and to confirm our empirical evidence.