Could Fecal Transplants Help with Weight Loss and Other Metabolic Issues?

Health Line

06-05-2025

Fecal transplants have been successfully used to treat gastrointestinal conditions. Researchers are currently studying whether they may also be used for weight loss and other metabolic issues.
A fecal microbiota transplant (FMT) is a procedure that transfers healthy donor stools into a person's intestines for therapeutic purposes. FMTs have been used in the United States since the 1980s.
The goal of an FMT is to help reset the bacteria in a person's gastrointestinal tract, which may then subsequently treat related conditions, such as ulcerative colitis (UC) and recurring Clostridioides difficile (C. diff) infections.
Researchers are discovering possible connections between gut microbiota imbalances and a variety of health conditions, including metabolic diseases and those associated with weight gain. Researchers theorize that FMT could possibly help treat these conditions.
While FMT is not considered a weight loss treatment, researchers are continuing to investigate the possible links between metabolic conditions and a disrupted gut microbiota.
This article takes a closer look at these potential connections and what current research has uncovered.
Can a fecal microbiota transplant from a lean donor reduce body weight?
Medical weight loss may be recommended for a number of metabolic diseases, including obesity and diabetes.
Some people might consider FMT if other treatments haven't worked, or if they don't want to use conventional medical interventions, such as weight loss medications or surgeries.
The idea here is that resetting the microbiota might help improve overall metabolism and weight loss.
What the research has found
Recent research suggests that FMT may have some benefits for treating obesity. According to one 2022 review, FMT may potentially reduce insulin resistance and high blood lipids that contribute to obesity.
However, the authors of the same clinical review also note that many clinical trials of FMT and metabolic disorders often do not succeed because of ineffective donors. This can make it challenging to discern whether FMT can benefit certain candidates for the treatment.
Separately, a 2023 meta-analysis reported that FMT could potentially improve both blood glucose and insulin in people with obesity, and possibly assist in weight loss.
The authors also found a correlation between a reduced body mass index (BMI) in participants with obesity and related metabolic diseases after undergoing FMT.
Nevertheless, the current literature still has mixed results. One 2022 randomized clinical trial on FMT and bariatric surgery found that FMT had no effect on weight loss from lean fecal transplant donors.
Can a fecal microbiota transplant be used for other metabolic diseases?
Metabolic diseases are conditions that are thought to develop due to metabolic dysfunction. Overweight and obesity are common examples. Other types of metabolic-related conditions include diabetes and multiple sclerosis (MS).
What the research has found
Several studies are currently being conducted on the role of FMT in MS and diabetes treatments, as well as other metabolic diseases.
However, other research has noted the possible long-term risk of developing metabolic issues after FMT, including obesity.
What health disorders have fecal microbiota transplants been used for successfully?
While the use of FMTs for metabolic disorders is still being investigated, this treatment does have a record of helping certain GI disorders, including C. diff infections and ulcerative colitis (UC).
FMT may help treat C. diff infections by restoring healthy bacteria in the gut microbiota. In particular, a doctor may recommend FMT as a second-line treatment when two rounds of antibiotics fail to clear the infection.
Some people may also need more than one course of FMT for recurring C. diff infections. Overall, the success rate is 94% after one or two treatments.
Fecal transplantation is also sometimes used in the treatment of UC. In these cases, treatment typically involves a total of four rounds of FMT. The exact success rate of FMT for UC is not as clear as it is for C. diff.
Possible future uses for FMT
It's not just weight loss and metabolic disorders that are being explored as candidates for FMT.
In fact, scientists are also looking at FMT as a possible emerging treatment for a broad spectrum of health issues, including liver disease, chronic fatigue syndrome, irritable bowel syndrome (IBS), mental health conditions, and more.
Potential drawbacks of FMT for metabolic disorders
While fecal transplants continue to be researched for treating a variety of conditions, there are also some drawbacks to consider.
First, while FMT is considered safe overall, the long-term effects are also unknown. The risk of drug resistance and other negative effects appears greater when proper screening of donor samples is not followed.
One 2021 review of FMT and its overall safety found that some of the possible short-term side effects included:
abdominal pain
bloating
gas
constipation
diarrhea
bloody stools
nausea
fever
bowel perforations
worsening GI disorder symptoms
Ironically, the same review found that obesity, inflammatory bowel disease (IBD), and IBS were all possible long-term adverse effects of FMT. Autoimmune diseases and fatalities were also noted.
Also, researchers are unclear whether transferring fecal samples could put recipients at risk of other microbiota-related conditions, such as diabetes.
What's more, these FMT treatments are expensive, ranging from $1,600 to $17,000 without insurance.
Takeaway
FMT is a procedure in which a fecal sample from a healthy donor is given to a person with an unhealthy microbiota.
Despite its success in treating C. diff and some cases of UC, scientists still do not fully understand how and why FMT works, and which microbes may be the most beneficial.
While early evidence suggests FMT may help people with metabolic issues lose weight and experience better insulin resistance, there isn't enough clinical backing for this to be a mainstream treatment just yet.