Changes in the composition and diversity of the gut microbiota have been observed following gastric bypass surgery (RYGB). This study assessed differences in the gut microbiota between individuals with severe obesity and individuals completing RYGB 12 years after surgery. An exploratory analysis of the effect of various metabolic health parameters on the gut microbiota was also performed.


Stool samples were collected 12 years after baseline from individuals completing RYGB (surgery group; N=16) and individuals with severe obesity that did not receive surgery (control; N=19) as part of the Utah Obesity Study. Metabolic health data were collected at baseline and then again at years two, six and twelve after surgery. The gut microbiota was quantified by sequencing the V4 region of the 16S rRNA marker gene. Significant differences in microbiota composition with RYGB and other covariates were determined by Unifrac distance analysis and PERMANOVA. Significant differences in the relative abundance of individual bacterial taxa were assessed using ANCOM.


The surgery group had higher relative abundances of Streptococcaceae 6.3±1.0% vs 3.2±0.8%) and Verrucomicrobiaceae (5.7±1.3% vs 1.1±0.3%), but lower relative abundances of Bacteriodaceae (8.8±1.8% vs 18.6±2.3%) 12 years after surgery. Age (p<0.05) and sex (p<0.01) also explained differences in the gut microbiota. Additionally, preliminary findings from the exploratory analysis revealed that the gut microbiota differed by lipid profile, weight, waist circumference, cardiovascular health, and sulfonylurea use.


The observed changes in the gut microbiota 12 years after RYGB are consistent with the environmental modifications of the gut and the shift in metabolic needs that occur following surgery. Although metabolic health changes following surgery are well documented, further investigation is needed to ascertain the role metabolic health parameters have in gut microbiota changes after surgery.