Probiotic Supplements After Bariatric Surgery

Do Probiotic Supplements After Bariatric Surgery Help Increase Weight Loss?

April 11, 2022

Our bodies contain more bacterial cells than actual human cells. Therefore, it is probably not surprising that our gut microbiome plays a role in many different body processes – likely more than we are even aware of. While it is well known that our microbiota plays an important role in our immune health and digestion, could it also play a role in weight loss? Could probiotic supplements after bariatric surgery assist with losing weight?

Probiotic Supplements After Bariatric Surgery

Much research has shown that there is a difference in the intestinal bacteria between obese and lean individuals. The two major categories of bacteria that have been examined are Bacteroidetes and Firmicutes.

Studies in mice have demonstrated higher levels of Firmicutes and lower levels of Bacteroidetes in obese mice, and the inverse (higher levels of Bacteroidetes and lower levels of Firmicutes) in lean mice. This theory was put to the test when Turnbaugh et al. transplanted the intestinal microflora from the lean mice to the obese mice and observed weight loss after the transplantation (

This has led to the theory that the alteration of gut bacteria could influence weight loss and/or promote a leaner body mass. (

One way in which this could be achieved is through the addition of probiotic supplements.

It is thought that the addition of probiotic supplements may play a role in preventing overweight and obesity by altering the gut ecosystem enough to improve energy metabolism and reduce overall inflammation.

To demonstrate how an alteration in gut bacteria may influence weight loss, a randomized controlled trial conducted in 2009 showed potential benefits after bariatric surgery with the addition of a probiotic supplement. The original goal of the study was actually to demonstrate that the addition of a probiotic could help to reduce bacterial overgrowth after bariatric surgery.

Reduction In Stomach Acid

Some of the factors involved in bacterial overgrowth after bariatric surgery are the reduction in stomach acid (since the acidity in the stomach and proximal small intestine helps to reduce the overgrowth of opportunistic or “bad” bacteria), and the lack of motility of the intestines (specifically in the bypassed part of the small intestine).

The treatment group of this study received 2.4 billion CFUs of Lactobacillus - a very common probiotic supplement at a relatively low dose. After treatment, the group that received the probiotic demonstrated greater weight loss for the first 6 months, but after that, no statistical significance was found between the groups. Additionally, the group receiving the probiotic supplement also had significantly higher vitamin B12 levels than the control group.

The reason for the improved vitamin B12 levels is thought to be due to the elimination of bacterial overgrowth with the administration of probiotics; since the extra bacteria in the small intestine may destroy the vitamin B12 (due to the lack of intrinsic factor) before it has an opportunity to be absorbed. (

While this study seems very promising, not all research within the past two decades has demonstrated such a beneficial effect. A meta-analysis examining the research on the addition of probiotics after bariatric surgery through March 2020 demonstrated a statistically significant difference in waist circumference, but not in overall weight loss, percentage of excess body weight loss, and BMI. (

Short-Term Improvement Of Gastrointestinal Symptoms

Another meta-analysis completed the same year demonstrated similar findings. The authors of the study found no significant differences in terms of excess body weight loss but did observe a short-term improvement of gastrointestinal symptoms with the addition of a probiotic supplement after bariatric surgery. Given the very low chance of adverse effects and potential minor improvements on weight loss, the authors did conclude that the addition of a probiotic supplement is worth considering. (

Another consideration is that after bariatric surgery there is an observed change in bacteria and gastrointestinal improvement in relation to the surgery itself. Therefore, it might be helpful to take a look at research in overweight and obese individuals that are not undergoing bariatric surgery. A systematic review and meta-analysis published in 2019 examining the effects of probiotics in controlling overweight/obesity did find improvements in weight loss, waist circumference, body fat loss, and metabolic indicators. (

Given these results, one might question whether the benefits of probiotics after bariatric surgery didn’t prove to be as statistically significant in the meta-analyses since bariatric surgery has such great improvements on metabolic health already.

Additionally, the research is not consistent in the type and strain of bacteria and/or probiotic that is used. For many of the meta-analyses discussed, it could be difficult to determine the true effect of probiotics since each individual research study used different probiotic supplements. Ultimately, the overall diversity of gut bacteria may be more important than one strain or group of bacteria. “In overweight/obese humans, low fecal bacterial gene richness is associated with more marked overall adiposity and dyslipidemia, impaired glucose homeostasis and higher low-grade inflammation” (  

Quick Changes In Digestive Function

Research has demonstrated that dietary patterns consisting of high-fat and high-sugar foods increase the abundance of Firmicutes (and decreases the amount of Bacteroidetes), whereas lower calorie, higher fiber diets have promoted an increase of Bacteroidetes.

Further, what is interesting is that it doesn’t take long for these changes to take effect in the intestines – many changes have been noted to occur within 24 hours of dietary changes. These observed changes not only improve digestive function, but also overall inflammation, metabolic health including insulin resistance, and changes to satiety hormones (such as an increase in GLP-1 and PYY).

Therefore, given the potential benefits of probiotic supplements and greater microbial diversity, the benefits of probiotic supplementation certainly outweigh any null side effects, but the overall composition of one’s diet needs to be considered as well. Supplementation is likely not going to outweigh poor food choices. Focusing on more high-fiber, minimally processed foods, and fewer calorie-, fat-, and sugar-dense foods will likely promote positive changes to the gut ecosystem and further benefit one’s metabolic health after bariatric surgery.

Michelle Bauche


Michelle Bauche, MS, RDN, LD, CSOWM is a registered dietitian working for Missouri Bariatric Services in Columbia, Missouri. She is a certified specialist in Obesity and Weight Management and a member of the Weight Management Dietetic Practice Group through the Academy of Nutrition and Dietetics. Read more articles by Michelle!