Background Prematurity and bronchopulmonary dysplasia can modify lung function in children and adults. Postnatal nutrition and rapid growth catch-up may influence the long-term development of lung function. Methods This prospective observational study was based on a cohort of 334 very-low-birth-weight (VLBW) neonates, born between 1 January 2008 and 12 December 2015. Patients with severe neurological damage, death or incomplete data record were excluded. When these infants reached a mean age of 7.7 years, a spirometry evaluation was performed, to determine FEV1, FEF25-75%, FVC and the FEV1/FVC ratio. The relation between these parameters and nutritional intake in the early neonatal period was determined by regression analysis. Results In total, 40 spirometry tests were performed. The results obtained, after adjusting for age and sex by Z-scores for the spirometry variables, showed that the schoolchildren who had been VLBW recorded significantly lower spirometry results (FVC, FEV1, FEF25-75%) than the reference values. Furthermore, there was a significant association between the FEV1/FVC ratio and the intake of macronutrients and energy in the first week of life. It is hypothesised that increasing energy intake and achieving a higher protein/energy ratio in the first week of life would improve the FEV1/FVC ratio by the time these VLBW infants reach school age. Conclusions Active nutritional management in the early neonatal period is associated with improved lung function, as reflected by the spirometry findings obtained.