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No benefit from faecal microbiota transplantation before bariatric surgery

Updated: Dec 29, 2022

Faecal microbiota transplantation (FMT) from a lean donor does not reduce body weight or improve the results of bariatric surgery among adults with severe obesity, according to a study led by researchers from Central Hospital in Lahti, Finland. The outcomes featured in the paper, ‘Effectiveness of Fecal Microbiota Transplantation for Weight Loss in Patients With Obesity Undergoing Bariatric Surgery - A Randomized Clinical Trial’, published in JAMA Network Open.

In their double-blinded, placebo-controlled, multicentre, randomised clinical trial adult individuals with severe obesity were treated at two bariatric surgery centres in Finland and included 18 months of follow-up. FMT from a lean donor or from the patient (autologous placebo) was administered by gastroscopy into the duodenum. Bariatric surgery was performed six months after the baseline intervention using laparoscopic Roux-en-Y gastric bypass (LRYGB) or laparoscopic sleeve gastrectomy (LSG). The main outcome was weight reduction measured as the percentage of total weight loss (TWL).

In total, 41 patients were recruited to participate in the study and were included in the final analysis (29 women [71.1%]; mean [SD] age, 48.7 [8.7] years; mean [SD] body mass index, 42.5 [6.0]). A total of 21 patients received FMT from a lean donor, and 20 received an autologous placebo. Six months after FMT, 34 patients underwent LRYGB and four underwent LSG. Thirty-four patients (82.9%) attended the last visit 18 months after the baseline visit.


The percentage of TWL at six months was 4.8% (95% CI, 2.7% to 7.0%; p<-.001) in the FMT group and 4.6% (95% CI, 1.5% to 7.6%; p=0.006) in the placebo group, but no difference was observed between the groups. At 18 months from the baseline (ie, 12 months after surgery), the percentage of TWL was 25.3% (95% CI, 19.5 to 31.1; p<0.001) in the FMT group and 25.2% (95% CI, 20.2 to 30.3; p<0.001) in the placebo group; however, no difference was observed between the groups.


The reduction in the mean BMI in the FMT group from baseline to the end of follow-up was 10.4 (95% CI, 8.2 to 12.5; p<0.001). In the placebo group, the change in BMI from baseline to the end of follow-up was 10.15 (95% CI, 7.8 to 12.5; p<0.001). The BMI at 6 months decreased 2.1 (95% CI, 1.2 to 3.1; p<0.001) in the FMT group and 1.3 (95% CI, −0.3 to 2.9; p=0.11) in the placebo group compared with the baseline.


From baseline to the end of follow-up, the mean weight was reduced by 25.3% (95% CI, 31.1% to 19.5%; p<0.001) in the FMT group and 25.2% (95% CI, 30.3% to 20.2%; p<0.001) in the placebo group; however, no difference was observed between the groups.


In this placebo-controlled, randomized clinical trial for obesity, significant changes in body weight were not observed in the 4 months after FMT or placebo administration. As expected, bariatric surgery 6 months after the baseline intervention reduced weight in both groups. From baseline to 6 months, as a result of the preoperative course of very low-calorie diet, percentage of TWL was 4.7%, and 1 year after the operation, the mean body weight of the whole study group was 25.3% lower than at the baseline without any differences between the groups.


“Our study provides further evidence that FMT alone is not sufficient to decrease body weight in humans. However, FMT may exert a transient effect on more delicate markers of metabolism,” the authors concluded. “In our trial, more variance in the postsurgical body weight loss was observed in the placebo group than in the FMT group; however, the difference was not significant.”2


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