According to Gram Research analysis, a 2026 systematic review of 10 studies involving 1,833 infants found that breastfed babies show different fat distribution patterns than formula-fed babies, with breastfeeding associated with more fat stored under the skin rather than deep in the belly. Where a baby stores fat during infancy may signal future metabolic health risks, though more research is needed to understand the long-term implications.
A new systematic review examined how different infant diets affect where fat builds up on babies’ bodies, not just how much total fat they have. Researchers looked at 10 studies involving 1,833 babies under 2 years old, using ultrasound to measure fat in different areas like the belly and arms. The findings suggest that breastfed babies may develop fat differently than formula-fed babies, with breastfeeding linked to more fat under the skin rather than deeper belly fat. This matters because where fat stores on a baby’s body could signal future health risks, making it important for parents and doctors to understand how early feeding choices influence fat distribution.
Key Statistics
A 2026 systematic review published in Nutrition Reviews examined 10 studies involving 1,833 infants and found that breastfed babies showed increased subcutaneous fat (fat under the skin) compared to formula-fed infants.
According to the systematic review, breastfeeding frequency and total human milk intake were associated with increased subcutaneous fat deposition in infants under 24 months old.
The review identified that only 3 of 10 studies directly compared fat distribution between breastfed and formula-fed infants, highlighting the limited research available on regional adiposity in babies.
Gram Research analysis found that 9 of the 10 studies reviewed were prospective cohort studies, with only 1 randomized controlled trial, indicating most infant fat distribution research relies on observational methods rather than controlled experiments.
The Quick Take
- What they studied: How different types of baby food (breast milk versus formula) affect where fat develops on infants’ bodies, measured using safe ultrasound imaging
- Who participated: 10 research studies involving 1,833 healthy babies between birth and 24 months old from various countries
- Key finding: Breastfed babies showed differences in fat distribution compared to formula-fed babies, with breastfeeding associated with more subcutaneous fat (fat under the skin) rather than visceral fat (deep belly fat)
- What it means for you: Where a baby stores fat during infancy may be an early sign of future metabolic health. Understanding these patterns could help doctors identify which babies might need extra attention for healthy growth, though more research is needed before making specific recommendations
The Research Details
This was a systematic review, which means researchers searched through thousands of published studies to find the best evidence on a specific topic. They looked through three major medical databases and found 10 studies that met their strict quality standards. Nine of these studies followed babies over time (called prospective cohort studies), and one was a randomized controlled trial where babies were randomly assigned to different feeding groups.
All the studies used ultrasound—the same safe imaging technology used during pregnancy—to measure fat thickness in different body areas. Researchers measured fat in the belly area (including both fat under the skin and deeper belly fat) and in the arms and legs. This approach is important because ultrasound is non-invasive, safe for babies, and gives precise measurements of fat in specific locations.
The researchers carefully evaluated the quality of each study using established scientific tools to make sure the evidence was reliable. They looked at factors like study design, sample size, baby ages, what babies were fed, and exactly where fat was measured.
Most infant health research focuses on total body weight and overall fat, but this review highlights that where fat is located on a baby’s body might be just as important. Deep belly fat (visceral fat) is linked to metabolic problems later in life, while fat under the skin (subcutaneous fat) appears less risky. By understanding how early feeding choices influence fat distribution, doctors could potentially identify babies at higher risk for future health problems earlier in life.
This systematic review included only 10 studies, which is a relatively small number, suggesting the research area is still developing. Most studies were observational (following babies without controlling their diet), with only one randomized controlled trial. The studies varied in how they measured fat, the ages of babies studied, and geographic locations, which makes it harder to draw firm conclusions. However, the researchers used rigorous quality assessment tools and transparent methods, which strengthens confidence in their findings.
What the Results Show
Three of the ten studies directly compared breastfed and formula-fed babies’ fat distribution. These studies found measurable differences in how fat was deposited between the two groups. Breastfed babies showed higher amounts of subcutaneous fat (the fat layer under the skin), while the pattern for deeper belly fat was less consistent across studies.
When researchers looked at specific aspects of breastfeeding, they found that babies who breastfed more frequently and received more total breast milk had increased subcutaneous fat. This suggests that the amount and frequency of breastfeeding may influence where a baby’s body stores fat.
The picture became more complicated when researchers examined specific nutrients in breast milk. Different studies found conflicting results about how proteins, fats, and carbohydrates in human milk affected regional fat distribution. Some nutrients showed associations with more fat in certain areas, while other studies found no clear pattern.
The review identified that most research has focused only on the liquid diet phase (breast milk and formula) in babies under 24 months. Very few studies examined how introducing solid foods affects fat distribution, which is an important gap since babies typically start solid foods around 6 months. The researchers also noted that fat distribution patterns varied depending on the baby’s age when measured, suggesting that timing of measurements matters for understanding these patterns.
This systematic review is among the first to specifically examine regional fat distribution in infants using ultrasound. Previous research mostly looked at total body fat or weight gain, without distinguishing where fat was stored. This review builds on growing evidence that fat location matters for health, a concept well-established in adults but less studied in infants. The findings align with emerging research suggesting that breastfeeding may have protective metabolic effects, though the mechanisms remain unclear.
The biggest limitation is that only 10 studies met quality standards, and most were observational rather than experimental. This means researchers couldn’t prove that diet directly causes fat distribution differences—other factors like genetics, activity level, or sleep could play a role. Studies used different ultrasound techniques and measured fat at different body locations, making direct comparisons difficult. Most research focused on liquid diets; almost no studies examined how solid food introduction affects fat distribution. Finally, the studies came from different countries with different populations, so findings may not apply equally to all babies worldwide.
The Bottom Line
Current evidence suggests that breastfeeding may influence where babies store fat, with associations to more subcutaneous fat. However, confidence in specific recommendations is moderate because research is still limited. Parents should continue following established infant feeding guidelines (exclusive breastfeeding for 6 months if possible, then introducing solids) based on broader health evidence. Healthcare providers should be aware that fat distribution, not just total weight, may provide useful information about infant metabolic health.
Pediatricians and infant health specialists should pay attention to this research as it develops, since understanding fat distribution could improve early health screening. Parents of infants should know this research exists but shouldn’t change feeding decisions based on these findings alone—the evidence is still developing. Researchers studying infant metabolism and long-term health outcomes should use these findings to design better studies. Public health officials developing infant nutrition guidelines may eventually use this information to refine recommendations.
Fat distribution patterns develop gradually during infancy, so changes wouldn’t be immediately visible. If a parent changed feeding practices based on this research, it would take weeks to months to see measurable differences in fat distribution on ultrasound. Long-term health benefits or risks from different fat distribution patterns may not become apparent until childhood or adulthood.
Frequently Asked Questions
Does breastfeeding affect where fat stores on a baby’s body?
Research suggests breastfeeding is associated with more fat stored under the skin rather than deep in the belly. A 2026 systematic review of 10 studies found breastfed infants showed different fat distribution patterns, though scientists need more research to understand why this happens and if it matters long-term.
Is belly fat in babies a sign of health problems?
Deep belly fat (visceral fat) is linked to metabolic problems in adults, and researchers believe it may signal similar risks in babies. However, current research on infant belly fat and future health is limited. Your pediatrician should monitor your baby’s overall growth and development.
How do doctors measure fat distribution in babies?
Ultrasound imaging—the same safe technology used during pregnancy—allows doctors to measure fat thickness in different body areas without radiation or discomfort. Researchers used ultrasound to examine fat in the belly and arms in the studies reviewed.
Should I change how I feed my baby based on this research?
No. Current evidence is still developing and limited. Continue following your pediatrician’s feeding recommendations based on established infant nutrition guidelines. Share this research with your doctor if you have concerns about your baby’s growth patterns.
What nutrients in breast milk affect baby fat distribution?
Studies showed conflicting results about how proteins, fats, and carbohydrates in breast milk influence where babies store fat. This inconsistency suggests more research is needed to understand which specific nutrients matter most for healthy fat distribution.
Want to Apply This Research?
- Track feeding method (breastfeeding frequency and duration, or formula amounts) alongside infant growth measurements and body composition data if available through healthcare provider. Record the specific timing and amounts to identify patterns over weeks and months.
- If using the app to track infant feeding, log daily breastfeeding sessions (duration and frequency) or formula intake amounts. This data can be shared with pediatricians to correlate with growth patterns and fat distribution measurements during routine check-ups.
- Use the app to maintain a consistent feeding log that can be reviewed with your pediatrician at regular wellness visits. Over time, this creates a detailed picture of feeding patterns that correlates with growth measurements, helping identify any concerning trends early.
This article summarizes research findings and is for educational purposes only. It does not constitute medical advice. Infant feeding decisions should be made in consultation with your pediatrician based on your baby’s individual health needs, medical history, and family circumstances. The research reviewed is still developing, and findings may change as more studies are conducted. Always follow your healthcare provider’s recommendations for infant nutrition and growth monitoring.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.