Gut bacteria is associated with reduced risk of obesity: evidence from the American Gut Project.

BACKGROUND

Gut bacteria has been shown an anti-obesity protective effect in previous studies and may be used as promising probiotics. However, the above effect may be confounded by common factors, such as sex, age and diets, which should be verified in a generalized population.

METHODS

We used datasets from the American Gut Project to strictly reassess the association and further examined the effect of aging on it. A total of 10,534 participants aged 20 to 99 years from the United States and the United Kingdom were included. The relative abundance of was assessed based on 16S rRNA sequencing data. Obesity (body mass index, BMI ≥ 30 kg/m) risks were compared across quintiles in logistic models with adjustment for common confounders. Restricted cubic splines were used to examine dose response effects between , obesity and age. A sliding-windows-based algorithm was used to investigate the effect of aging on -obesity associations.

RESULTS

The median abundance of was 0.08% (interquartile range: 0.006-0.93%), and the prevalence of obesity was 11.03%. Nonlinear association was detected between and obesity risk ( = 0.01). The odds ratios (95% confidence interval) for obesity across the increasing quintiles (referencing to the first quintile) were 1.14 (0.94-1.39), 0.94 (0.77-1.15), 0.70 (0.56-0.85) and 0.79 (0.64-0.96) after adjusting for age and sex ( for trend < 0.001). This association remained unchanged after further controlling for smoking, alcohol drinking, diet, and country. The odds ratios (95% CI) of were 0.19 (0.03-0.62) and 0.77 (0.64-0.91) before and over 40 years, respectively, indicating that the protective effect of against obesity was not stable with aging.

CONCLUSION

High relative abundance of is associated with low risk of obesity and the association declines with aging.