Longer breastfeeding duration may protect against obesity in early childhood, while early introduction of solid foods may increase the risk for obesity, according to study results published in Pediatric Obesity.
Previous studies have reported inconsistent findings on the effects of early feeding practices on obesity. Furthermore, most of these studies have examined the effect of early infant feeding on obesity at a single time point. The goal of the current study was to explore the effects of breastfeeding duration and timing of solid food introduction on body mass index (BMI) z score trajectories across the first 5 years of life.
The researchers conducted a secondary analysis of longitudinal data from the Melbourne Infant Feeding, Activity and Nutrition Trial (InFANT) Program, a randomized controlled trial that was aimed at reducing infant obesity risk behaviors in children aged 3 to 18 months, with follow-up until age 5 years.
The study included 542 children at baseline (approximate age, 3 months) who were followed up at approximately 9, 18, 42, and 60 months of age. The analysis included 483 children with ≥2 BMI z score measures and complete data on breastfeeding duration and timing of solid food introduction. Most children (59.2%) were breastfed for ≥6 months and a higher percentage (64.6%) had solid food introduced before age 6 months.
BMI z score at birth was similar in children who were breastfed for ≥6 vs <6 months. Over time, however, BMI z scores differed between the groups: children who were breastfed for ≥6 months had lower mean BMI z scores at all ages between 3 and 60 months than children who were breastfed for <6 months, with adjusted mean differences in BMI z score of -0.34, -0.44, -0.13, -0.10, and -0.23 at 3, 9, 18, 42, and 60 months, respectively (P <.001). Children with breastfeeding duration ≥3 vs <3 months had lower BMI z scores at 3 and 9 months, but no significant difference in BMI z score was noted at a later stage.
As for timing of solid food introduction, mean BMI z score at 18 and 42 months was higher in children who had solids introduced before vs after 6 months of age (P <.001), but this association was not significant after adjustment for child and maternal factors.
When the researchers combined the duration of breastfeeding with the timing of solid food introduction, they found that children who were breastfed for ≥6 months had lower average BMI z scores from 3 to 60 months than children who were breastfed for <6 months, whether solid foods were introduced before or after 6 months of age.
The researchers acknowledged several study limitations, including the observational design and lack of adjustments for children’s intake of energy-dense and nutrient-poor foods, physical activity, sedentary behavior, and sleep patterns. Further limitations included loss to follow-up, missing data, and inability to separate exclusive breastfeeding from any breastfeeding.
“[Our] findings provide further support for infant feeding guidelines to promote breastfeeding of at least 6 months duration to promote healthy growth,” concluded the researchers.
Zheng M, Cameron AJ, Birken CS, et al. Early infant feeding and BMI trajectories in the first 5 years of life. Obesity (Silver Spring). 2020;28(2):339-346.