Research into the relationship between body weight and the developing brain has often focused on older children and adolescents. New findings from Florida International University suggest that measurable associations may already be present much earlier, including during the preschool years.
Using an advanced form of magnetic resonance imaging, researchers examined brain microstructure in 159 children between ages 4 and 7. Higher body mass index, or BMI, was associated with differences in several regions involved in reward, motivation, taste, and hunger, raising new questions about when brain and body weight begin to become connected during development.
Looking at the Brain Earlier in Childhood
The research, published in Scientific Reports, used restriction spectrum imaging, or RSI, to examine subtle characteristics of brain tissue. RSI allows researchers to study patterns of water diffusion within tissue, providing information about microstructure that may not be visible with more conventional imaging approaches.
The children were part of a larger research program at Florida International University. The analyzed group included 81 children with attention-deficit/hyperactivity disorder and 78 typically developing children, giving researchers an opportunity to examine whether ADHD altered the relationship between body composition and brain structure.
Researchers compared the imaging results with several measures related to body composition, including age- and sex-adjusted BMI z-score, waist circumference, body fat percentage, and obesity status. Of those measures, significant brain associations emerged specifically with BMI z-score.
Where the Differences Appeared
Higher BMI z-scores were associated with differences in several regions connected with reward and salience processing. These included the anterior insula, nucleus accumbens, putamen, pallidum, and hippocampus, while an exploratory analysis also identified a signal in the hypothalamus.
These regions participate in different but overlapping functions. The nucleus accumbens is heavily involved in reward and motivation, while the insula contributes to taste, internal body awareness, and determining which sensations or experiences receive attention. The hypothalamus has an important role in regulating processes that include hunger and energy balance.
The finding involving the insula was particularly notable because similar research in older children had not produced the same pattern. Seeing an association at ages 4 to 7 suggests that some relationships between body composition and brain development may become detectable earlier than previous research had established.
What the Imaging Cannot Yet Tell Researchers
The MRI results should not be interpreted as evidence that researchers have identified a neurological cause of childhood obesity. RSI measures characteristics of tissue indirectly, and the biological processes behind the observed differences remain uncertain.
The researchers discuss neuroinflammation as one possible explanation for some of the imaging patterns, but other developmental mechanisms are also plausible. The imaging measure itself cannot establish that inflammation is occurring, which is why future studies combining brain scans with direct metabolic and inflammatory measurements will be important.
The study also captured each child at one point in time. That means researchers cannot determine whether changes in BMI preceded the brain differences, whether the brain differences appeared first, or whether both developed in response to other biological, behavioral, or environmental factors.
That distinction matters because an association can point researchers toward a question without providing the answer. Longitudinal research that follows the same children as they grow will be needed to understand how these relationships change over time.
ADHD Did Not Strengthen the Association
The researchers had expected ADHD to potentially influence the relationship between BMI and brain microstructure. ADHD has been associated with differences in some of the same reward-related systems being investigated, and behaviors such as impulsivity have also been studied in relation to eating and body weight.
Instead, ADHD diagnosis did not significantly change the BMI-related brain associations. Children with ADHD and typically developing children showed a broadly similar pattern, suggesting that the observed relationship was not specific to the ADHD group within this sample.
The composition of the study is still important when interpreting the findings. More than half of the participating children had ADHD because the sample came from a broader clinical research program, so replication in larger independent groups will help establish how widely the findings apply.
Why the Age of the Children Matters
Much of the earlier neuroimaging work connecting body composition with reward-related brain systems has involved older children or adolescents. Detecting related patterns between ages 4 and 7 moves the scientific question into a period when the brain, behavior, eating habits, and many other developmental systems are changing rapidly.
It does not mean that brain imaging is ready to identify which preschool children will later develop obesity. Instead, the research provides another piece of evidence that the biological relationships associated with body weight may begin forming well before adolescence.
For professionals who work with young children, the broader developmental perspective is useful. Physical growth, behavior, cognition, sensory experiences, and brain development do not occur independently, and research increasingly examines how these systems interact rather than treating them as separate processes.
An Early Finding, Not a Reason to Change Care
The researchers caution against using these findings as a reason for parents to change a child's nutrition or physical activity based on brain imaging results. The study examined developmental associations rather than testing an intervention, so it does not establish a new approach to clinical care.
One unanswered question is why BMI z-score was associated with the imaging findings while waist circumference and body fat percentage were not. The researchers note that body fat and waist measurements can be more difficult to collect consistently in very young children, meaning measurement constraints may have contributed to the difference.
The research team plans to follow children over time to investigate whether changes in brain microstructure appear before or after changes in body weight and to incorporate measures of metabolism and inflammation that may clarify the underlying biology. Until those longitudinal data are available, the findings are best viewed as evidence that associations between body composition and brain microstructure can be detected early in childhood, while their direction, mechanism, and long-term significance remain unresolved.
Sources
- Florida International University via News-Medical. โHigher BMI linked to brain differences in preschool children.โ September 22, 2026.
- Bayat, M., Braun, B., Curzon, M., et al. โRestriction spectrum imaging reveals brain microstructural correlates of obesity risk in early childhood.โ Scientific Reports. Published July 13, 2026.
