Within a narrow age range and shared environment, gut microbiota composition is broadly similar regardless of BMI and dietary patterns in Mexican preschool-aged children, highlighting the complexity of microbiota-host interactions in early childhood.
Key Findings
Methods
The study characterized gut microbiota of 84 preschool children aged 3 to 5 from semi-urban and urban areas in Veracruz, Mexico, classified by BMI into underweight, normal weight, or overweight/obese groups.
Cross-sectional study design with n=84 preschool children
Age range: 3 to 5 years
Participants were from semi-urban and urban areas in Veracruz, Mexico
BMI classification into underweight (UW), normal weight (NW), and overweight/obese (OW) groups
Fecal samples were analyzed using 16S rRNA gene sequencing; perinatal and early-life exposures retrieved retrospectively using a validated, interviewer-administered questionnaire
Results
Clinical factors such as prematurity and early feeding showed weak associations with BMI.
Perinatal and postnatal factors evaluated included prematurity and early feeding practices
Associations between these clinical factors and BMI were described as weak
Data on early-life exposures were collected retrospectively via validated questionnaire
Results
Dietary patterns across BMI groups exhibited general homogeneity, consistent with a Western diet, with no significant differences in relation to BMI.
All BMI groups showed a broadly Western dietary pattern
No statistically significant differences in dietary patterns were observed between BMI categories
Current dietary patterns were evaluated alongside anthropometric measurements
Results
The predominant bacterial phyla across all BMI groups were Bacillota and Bacteroidota.
Both Bacillota (formerly Firmicutes) and Bacteroidota (formerly Bacteroidetes) were the dominant phyla regardless of BMI classification
No significant differences in the relative abundance of major phyla were observed between BMI groups
Phylum-level composition was broadly similar across underweight, normal weight, and overweight/obese children
Results
Alpha diversity showed significant differences according to BMI categories, while beta diversity did not differ significantly between groups.
Alpha diversity (within-sample diversity) was significantly different across the three BMI categories
Beta diversity (between-sample diversity) showed no significant differences between BMI groups
This pattern suggests variability in individual microbial richness/evenness by BMI without corresponding shifts in overall community composition
Results
At the family level, Prevotellaceae was more abundant in underweight children and Lachnospiraceae was more prevalent in children with higher BMI, though these trends were not statistically significant.
Prevotellaceae showed a trend toward higher relative abundance in the underweight group
Lachnospiraceae showed a trend toward higher relative abundance in the overweight/obese group
Neither trend reached statistical significance
These family-level observations were noted as non-significant trends rather than confirmed associations
Discussion
Within a narrow age range and shared environment, gut microbiota composition was broadly similar regardless of BMI and dietary patterns.
The study population shared semi-urban and urban environments in the same Mexican state
The narrow age range (3–5 years) and shared environmental context may have contributed to the lack of significant microbiota differences by BMI
Authors conclude that 'gut microbiota composition is broadly similar regardless of BMI and dietary patterns' in this cohort
Authors highlight 'the complexity of microbiota-host interactions in early childhood'
Conclusions
Further studies integrating functional analyses are needed to clarify causal links between gut microbiota and a child's weight status.
The cross-sectional design limits causal inference
16S rRNA gene sequencing provides taxonomic but not direct functional data
Authors recommend integration of functional analyses in future research
The study underscores the need to go beyond compositional assessments to understand microbiota-BMI relationships in early childhood
What This Means
This research studied the gut bacteria (microbiota) of 84 Mexican preschool children between ages 3 and 5, comparing children who were underweight, normal weight, or overweight/obese. The researchers collected stool samples and analyzed which bacteria were present using genetic sequencing, while also gathering information about the children's birth history, feeding as infants, and current diets. The main finding was that, despite differences in body weight, the overall community of gut bacteria looked very similar across all three weight groups, and the children's diets were also broadly similar, reflecting a typical Western-style eating pattern.
The researchers did find that a measure of bacterial diversity within individual samples (alpha diversity) differed significantly between weight groups, and there were hints that certain bacterial families — Prevotellaceae in underweight children and Lachnospiraceae in heavier children — appeared at different levels, but these family-level differences were not statistically significant. Early-life factors like premature birth and type of early feeding had only weak links to body weight in this group.
This research suggests that in young children living in similar environments and eating similar diets, body weight alone may not strongly predict the makeup of gut bacteria at this stage of childhood. The authors note that studying children of the same age in the same region likely reduced variation that might be seen in more diverse populations, and that future studies should examine what these bacteria are actually doing functionally, not just which ones are present, to better understand how gut bacteria might be connected to children's weight and health.
Hernández-Rodríguez D, Contreras A, Melgar Lalanne G, Lara Arellano S, Meza J, Licona Cassani C, et al.. (2026). Fecal microbiota composition concerning body mass index and early-life factors in Mexican preschool-aged children: a cross-sectional study.. PeerJ. https://doi.org/10.7717/peerj.21253