Association Between Gut Microbiota Diversity and Body Mass Index (BMI) in Healthy Young Adults in the United States: Insights Into the Gut-Brain-Metabolic Axis Using the Curated Metagenomic Data

BACKGROUND: Emerging evidence suggests that gut microbiota diversity plays a critical role in metabolic regulation and may influence body mass index (BMI). However, findings in healthy populations remain inconsistent. OBJECTIVE: This study aims to determine whether gut microbiota alpha-diversity is associated with BMI among healthy young adults aged 18-39 years in the United States and to explore potential implications for the gut-brain-metabolic axis. METHODS: This cross-sectional study utilized publicly available metagenomic data from the CuratedMetagenomicData repository. After preprocessing in R version 4.5.0 (R Foundation for Statistical Computing, Vienna, Austria), data were analyzed using Stata version 18 (Released 2023; StataCorp LLC, College Station, TX). Alpha-diversity indices (Shannon, Simpson, and Richness) were computed and examined across BMI categories (normal, overweight, and obese) using one-way analysis of variance (ANOVA) and chi-square tests. Linear regression models were employed to assess associations between BMI and diversity measures, adjusting for age and gender. RESULTS: Among 147 participants, BMI differed significantly across weight categories (p < 0.001), but no significant association was observed between Shannon diversity and BMI (p = 0.527). Age emerged as the only significant predictor of BMI in adjusted models (p < 0.001). CONCLUSION: Gut microbial alpha-diversity was not significantly associated with BMI among healthy young adults. Functional microbial characteristics, rather than diversity alone, may better explain variations in metabolic status.