Firmicutes/Bacteroidetes Ratio as an Insufficient Indicator of Metabolic Status in Mexican Young Adults

Background: The Firmicutes/Bacteroidetes (F/B) ratio has been proposed as a microbial biomarker of obesity and metabolic alterations; however, its reliability remains controversial, particularly in young populations. Methods: This study evaluated the relationship between the F/B ratio, body fat percentage, and metabolic markers in 70 university students aged 18–25 years, classified as normal weight (29.5%), overweight (27.4%), or obese (43.2%). Anthropometric measurements and biochemical parameters (glucose, triglycerides, total cholesterol, and HDL-C) were obtained using standard methods, and stool samples were analyzed to determine the F/B ratio. Results: Mean glucose and cholesterol were within normal ranges, whereas triglycerides showed high variability, and HDL-C was lower in men. Although the F/B ratio increased across nutritional groups, regression analyses showed weak correlations (R < 0.5) and no significant associations (p > 0.05). Conclusions: The F/B ratio is not an adequate standalone indicator of metabolic status in Mexican young adults.