Abstract:
In turn, the human gut microbiota (GM) has emerged as a major regulator of digestion and metabolism, immunity and intestinal barrier maintenance, and it is altered in metabolic disorders associated with obesity. Emerging evidence shows associations between specific microbiota compositions and anthropometric measures of adiposity, such as BMI, waist circumference and body fat distribution. Concurrently, age, early-life exposures, diet, lifestyle and ethnicity strongly modify both gut microbiota composition and obesity risk, making this relationship highly entangled and context-specific. The objective ofthis article was to summarise recent literature regarding the association between gut microbiota composition and anthropometric markers ofobesity in adults. Materials and methods. Articles published in the last 10 years in PubMed, Scopus and Google Scholar were reviewed using a narrative review approach; based on the relevance of their content and keywords, studies focusing on gut microbiota-anthropometry associations in humans were selected. The studies examined consistently show relationships between the abundance of specific bacterial taxa, overall microbiota diversity and anthropometric measurements such as BMI, waist circumference, waist-to-hip ratio and body fat percentage. Beyond body weight, diet quality is a major determinant ofboth microbiota composition and adiposity, with healthier dietary patterns being associated with more favourable microbial profiles, independent of body size. Evidence on metabolically healthy obesity suggests that people with similar anthropometric measures yet markedly different microbiota profiles may exhibit highly contrasting metabolic phenotypes. Data from extreme nutritional states (anorexia nervosa, athletes and overweight/obesity) demonstrate that microbiota status reflects more than total body weight; it captures deeper aspects ofbody composition, such as the relative proportions oflean and fat mass. Studies from different regions ofthe world show that national and ethnic background, traditional diet and social determinants contribute to shaping 2625 “regional” microbiota signatures of obesity, while fungal-bacterial interactions and physical activity further add to this complexity. Methodological heterogeneity (including different sequencing platforms, analytical pipelines and definitions of obesity), together with the predominance of cross-sectional designs, challenges comparability of results and does not allow confirmation of causality. In summary, available evidence suggests a consistent yet heterogeneous relationship between gut microbiota and obesity in adults, substantially moderated by age, sex, dietary type and quality, metabolic profile, ethnicity and lifestyle characteristics. Additional robust prospective and interventional studies with standardised microbiota assessment and detailed anthropometric phenotyping are essential to elucidate causal pathways and to identify valid, reliable, population-specific microbial biomarkers for obesity and its cardiometabolic risk.
