LAUSR

We read, with interest, Pluymen et al.’s paper describing whether infants who were fed complementary foods before 4 months had higher odds of becoming overweight compared with children who were breastfed until 4 months (the PIAMA Birth Cohort Study) [1]. The study was impressive as it followed children for 17 years. The topic is important as 8–15% of Dutch infants [2] and 20–40% of United States infants [3] are given complementary feeding before the widely recommended age of 4 to 6 months [4]. The authors concluded that infants fed formula or breast milk for fewer than 4 months had a higher incidence of being overweight during the ages of 3 months to 17 years compared with those fed exclusively breast milk up to 4 months of age. The authors adjusted for several potential confounders that could impact the relationship between early introduction of complementary feeding and child overweight, including sex, maternal age at birth, maternal education level, and birth weight. However, this study could be strengthened by adjustment for several other key confounders: physical activity, parental BMI, and energy intake during childhood. Physical activity is important as several studies have found a statistically positive correlation between increased child physical activity and lower BMI [5]. The Dutch Physical Activity Questionnaires for children and adolescents could be used for data collection [6]. Parental BMI has also been shown to be a risk factor for child overweight and obesity [7] and could have been assessed when the child weight and measurements were obtained. Energy intake over childhood has also been shown to be an important determinant in childhood overweight and obesity [8], and is therefore, a potential confounder. This could have been assessed using a food frequency questionnaire completed by parents when children’s height and weight were measured (1, 8, 11, 14, 17 years).