Feeding patterns and growth trajectories in breast-fed and formula-fed infants during the introduction of complementary food.

Introduction: several investigations have identified breastfeeding as a protective factor for rapid infant weight gain and childhood obesity while other studies have found that this protective effect could be the result of confounding factors. Objectives: to assess the associations between lactation practices (breast-fed vs formula-fed infants) during the introduction of complementary food period, as well as the following: a) patterns of food intake; and b) trajectories of growth at six, nine and 12 months (z-score of weight, height and body mass index [BMI] and changes in these z-scores from six to 12 months). Methods: two hundred and three infants randomly selected from Spanish Primary Health Centres were measured. Parents recorded all infant's food consumption for three days (g/day). Linear regression models were applied. Results: breast-fed infants had a lower intake of cereals, fruit baby food, vegetables with meat/fish and a total intake of food compared to formula-fed infants at nine months of age. After adjusting for sex, parental education and total food intake, breastfed children continued to have lower intake of cereals (-5.82, 95% CI: -9.22, -2.43), and lower total food intake (-301.23, 95% CI: -348.50, -253.96). Breast-fed infants had a lower change in z-score of weight, height and BMI from six to 12 months of age and these differences remained when adjusting for all confounders. Conclusions: formula-fed infants during the complementary feeding period have a higher food intake and show higher rates of rapid infant weight gain compared to breast-fed infants. These differences in growth trajectories depending on breastfeeding maintenance and food intake during early life must be considered in adiposity risk evaluation.