Probiotics Improve Outcomes After Roux-en-Y Gastric Bypass Surgery

Clinical Study Highlight

Probiotics Improve Outcomes After Roux-en-Y Gastric Bypass Surgery: A Prospective Randomized Trial.

J Gastrointest Surg. 2009 Apr 18. [Epub ahead of print]

Woodard GA, Encarnacion B, Downey JR, Peraza J, Chong K, Hernandez-Boussard T, Morton JM.

The possible role of probiotics in weight management has been greatly hyped, ever since initial observations by scientists at Washington University identified a microbiota that appeared to be characteristic of obese people (Ley, et al. 2006. Human gut microbes associated with obesity. Nature 444:1022-3). However, there are few intervention studies documenting that probiotics might contribute to improved weight status in obese individuals. Woodard et al. (2009) hypothesized that probiotic treatment would improve gastrointestinal outcomes after bypass surgery. The gastric bypass procedure may disrupt several parameters of intestinal function including gastric acid secretion, intestinal motility and increased bacterial overgrowth, which can lead to increases in gastrointestinal symptoms such as abdominal pain, bloating, flatulence and diarrhea.

The study design was randomized and blinded, but although a control group was included, it was not placebo-controlled. Forty-four morbidly obese subjects were recruited into the study. Primary endpoints included breath hydrogen levels (indicative of bacterial overgrowth) and gastrointestinal-related quality of life. Data on serologies and weight loss were also collected. Measurements were conducted before surgery and at 3 and 6 months after surgery. Among other medications typical for this group of patients, subjects received or didn’t receive a 6 month supply of Puritan’s Pride® probiotic supplement with Lactobacillus species (2.4 x 109/d, at time of manufacture).

Results showed that at 3 and 6 months postoperatively a reduction in breath hydrogen was observed with the probiotic group, but not the control group. This suggests that bacterial overgrowth was less of a problem for patients taking probiotics. Both groups showed equivalent improvement in gastrointestinal quality of life scores compared to preoperative scores. Perhaps most interestingly, the probiotic group lost significantly more weight postoperatively than the control group, measured as % excess weight loss:


  • 6 weeks: probiotics=29.90% vs. controls=25.50%, p=0.0577
  • 3 months: probiotics= 47.68% vs. controls=38.55%, p value 0.0222
  • 6 months: probiotics=67.15% vs. controls=60.78%, p=0.2730


Differences were statistically significant only at the 3 month postoperative measurement.

This study suggests that this probiotic product might improve outcomes related to bacterial overgrowth and possibly increase weight loss for this group of surgery patients.

Taken as a whole, this study has some methodological weaknesses which prevent strong conclusions, especially with regard to the impact of probiotics on weight loss. It is a small study, not powered for weight loss as a primary endpoint. No assessments were conducted on colonizing microbiota, so it is not clear if this result is related to microbiota changes. The test groups weren’t matched: the probiotic group was statistically significantly older and higher rate of diabetes on intake; furthermore, the percent of subjects with bacterial overgrowth was just over 15% in the probiotic group and just under 5% in the control group – a non-significant difference, but perhaps still relevant as this was a key study outcome. In addition, the control group trended toward higher BMI (49.6 vs. 45.7, p=0.0946) and total weight (306.4 vs. 276.6, p=0.0512) at intake. Regrettably, the test product was inadequately described; the product was described only to the genus level and microbiological assessment of the viable numbers of probiotic in the product at time of use were not conducted (only at time of manufacture).

As the authors indicate, the positive results obtained in this study provide a strong basis for conducting a follow up study without the indicated weaknesses.