The Effects of Diet on Regional Adiposity Measured via Ultrasound in Full-Term Infants: A Systematic Review

Abstract Context While total body fat is an important metric of infant growth, regional adiposity may provide more clinically relevant information for predicting metabolic health risk compared with total body fat alone. Regional adiposity assessment in infants remains limited, in part due to historical challenges in accurately and safely assessing adiposity in early life. Ultrasonography has emerged as a practical and non-invasive assessment method to examine the impact of infant diet on fat distribution. Objective The objective of this study was to systematically review the existing evidence on the use of ultrasound to synthesize the impacts of infant diet on regional adiposity in infants of between 0 and 24 months. Data Sources A comprehensive literature search was conducted in PubMed, Web of Science, and CINAHL, identifying 530 articles. Data Extraction Three reviewers independently extracted data, including study design, sample size, infant age, dietary exposure, site of fat measurement, and adipose tissue thickness. Quality was assessed using ROBINS-I (non-randomized) and ROB-2 (randomized trial). Data Analysis Ten studies involving 1833 infants met the inclusion criteria (9 prospective cohort studies and 1 randomized controlled trial). All studies focused on the liquid diet phase (breast milk, infant formula) and used the same technique to measure the abdominal (visceral fat, subcutaneous fat, and/or preperitoneal fat) or limb areas (triceps, biceps, arms, subscapular, suprailiac, and/or thighs). Three studies reported differences in subcutaneous and visceral fat deposition between breastfed and formula-fed infants. Breastfeeding frequency and total human milk intake were associated with increased subcutaneous fat, while macronutrients in human milk had conflicting associations with regional adiposity. Conclusions The effects of dietary exposures during infancy on regional adiposity identified in this review, including subcutaneous vs visceral fat, vary, possibly due to the heterogeneity in study characteristics, including age and geographic location. Future research should examine how early feeding practices, including complementary food introduction and composition, influence regional adiposity. Systematic Review Registration PROSPERO registration No. CRD420251180472.