Body composition estimates are widely used in clinical research and field studies as measures of energy-nutrient balance, functionality and health. Despite their broad relevance and multiple applications, important gaps remain in techniques available for accurately and precisely quantifying body composition in infants and children from birth through 5 years. Identifying these gaps and highlighting research needs in this age group were the topics of a National Institutes of Health workshop held in Bethesda, MD, USA, 30-31 May 2019. Experts reviewed available methods (multicompartment models, air-displacement plethysmography, dual-energy X-ray absorptiometry, weightlength and height indices, bioimpedance analysis, anthropometry-skinfold techniques, quantitative magnetic resonance, optical imaging, omics and D3-creatine dilution), their limitations in this age range and high priority research needs. A summary of their individual and collective workshop deliberations is provided in this report.

The first week after birth is a critical time for the establishment of microbial communities for infants. Preterm infants face unique environmental impacts on their newly acquired microbiomes, including increased incidence of cesarean section delivery and exposure to antibiotics as well as delayed enteral feeding and reduced human interaction during their intensive care unit stay. Using contextualized paired metabolomics and 16S sequencing data, the development of the gut, skin, and oral microbiomes of infants is profiled daily for the first week after birth, and it is found that the skin microbiome appears robust to early life perturbation, while direct exposure of infants to antibiotics, rather than presumed maternal transmission, delays microbiome development and prevents the early differentiation based on body site regardless of delivery mode. Metabolomic analyses identify the development of all gut metabolomes of preterm infants toward full‐term infant profiles, but a significant increase of primary bile acid metabolism only in the non‐antibiotic treated vaginally birthed late preterm infants. This study provides a framework for future multi‐omic, multibody site analyses on these high‐risk preterm infant populations and suggests opportunities for monitoring and intervention, with infant antibiotic exposure as the primary driver of delays in microbiome development.

Maternal feeding is a frequent intervention target for the prevention of early childhood obesity but longitudinal associations between feeding and child overweight are poorly understood. This observational cohort study sought to examine the cross-lagged associations between maternal feeding and overweight across ages 21, 27, and 33 months. Feeding was measured by maternal self-report (n=222) at each age. Child weight and length were measured. Cross-lagged analysis was used to evaluate longitudinal associations between feeding and overweight, adjusting for infant birth weight, maternal body mass index, maternal education, and maternal depressive symptoms. The sample was 50.5% white, 52.3% male and 37.8% of mothers had a high school education or less. A total of 30.6%, 29.2%, and 26.3% of the sample was overweight at each age, respectively. Pressuring to Finish, Restrictive with regard to Amount, Restrictive with regard to Diet Quality, Laissez-Faire with regard to Diet Quality, Responsiveness to Satiety, Indulgent Permissive, Indulgent Coaxing, Indulgent Soothing, and Indulgent Pampering each tracked strongly across toddlerhood. There were no significant associations between maternal feeding and child overweight either in cross-sectional or cross-lagged associations. Our results do not support a strong causal role for feeding in childhood overweight. Future work longitudinal work should consider alternative approaches to conceptualizing feeding and alternative measurement approaches.

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Infant obesity and the rate of weight gain during infancy are significant public health concerns, but few studies have examined eating behaviors in infancy. Food cue responsivity has been described as a key contributor to obesity risk in school age children and adults, but has been rarely examined during infancy. The purpose of the current study was to test among 30 infants aged 6 to 12 months the hypotheses that infants would show greater interest in food versus nonfood stimuli, and that greater birth weight, greater rate of weight gain during infancy, greater mother-reported food responsiveness, being formula versus breastmilk fed, and higher maternal body mass index, would each be associated with greater interest in the food versus non-food stimulus. Results showed that overall infants showed a preference for the food versus non-food stimulus. Preference for the food versus non-food stimulus was predicted by greater infant rate of weight gain since birth, greater maternal-reported infant food responsiveness, and having been exclusively formula-fed, but not by any other factor tested. Results are discussed with regard to theoretical implications for the study of infant obesity and applied prevention implications.