Stool transplants- a new dawn for obesity treatment?

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60 second summary

  • Stool transplants are also known as fecal microbial transplants (FMT’s)
  • They involve the transfer of stool from a healthy individual to the intestines of an ill person
  • Microbes present in the stool colonise the ill persons gut and have the potential to restore balance
  • Studies in mice have shown FMT’s can reverse obesity

Treating obesity with a stool transplant

The past few centuries have seen a rapid incline in metabolic disorders, amongst others- type 2 diabetes, hypercholesterolemia (high cholesterol) and heart disease. It is recently emerging that aside from genetic, lifestyle and environmental factors, the microbes residing in the gut play a large role in the regulation of these maladies.

Studies in mice have shown that there is more to altering a person’s microbial make-up than just by diet which only accounts for 57% of variation- other lifestyle alterations such as feeding patterns and sleep cycles also play a large role.

Main modifications

Modification of a persons microbiome can be achieved through 3 main interventions-

  1. Taking prebiotics such as dietary fiber
  2. Taking probiotics- so beneficial bacteria
  3.  Fecal transplant

Fecal microbiota transplant- transfer of stool from a donor to the  intestines of a recipient to restore bacterial balance. [1]

Fecal transplant intervention

This procedure has been used since the 4th century in the treatment of Clostridium difficile (diarrhea)  where in the Chinese Dong-jin dynasty administration of a stool suspension by mouth to patients with diarrhea yielded positive results.[2] Fecal transplantation is an alternative to antibiotic treatment with some studies showing a 91% primary cure rate. The procedure involves the transplant liquid being administrated into your large intestine through the anus.

Endoscope- a long thin flexible tube used inserted into the body

Fecal transplants and obesity

One area of recent interest has been the treatment of obese individuals with faecal transplants from their lean counterparts. So far, studies have suggested that microbes in the obese, thought to be of the phylum Firmicutes, are more effective at extracting energy from foods. Associations have been made between the increase of Firmicutes bacteria and decreased Bacteroidetes with increasing body mass index. (BMI)[3]

BMI- measure that uses your height and weight to work out if your weight is healthy.[4]

Experiments have found correlations between an increase in Bacteroides and weight loss[5] therefore it seems viable to suggest that altering one’s microbiome through a fecal transplant could potentially have therapeutic and potentially curative effects.

How would a fecal transplant cure obesity?

The first question to answer is what is the cause of obesity? Despite this having a variety of plausible answers one of the most plausible is insulin resistance.

Insulin resistance- when your body doesn’t respond properly to the hormone insulin which is important in removing glucose from your bloodstream into storage.

People suffering with obesity hare said to have low insulin sensitivity which means larger doses of insulin are required to lower blood glucose than in a healthy individual. In studies obesity and insulin resistance in rats has been reversed with fecal microbial transplants.

The scientific mechanisms for this dramatic change is still in question, but 1 thing is known for sure- Microbes play a large role in metabolism of glucose and fat, and this is through a protein found in the liver and intestines called the Farnesoid X receptor (FRX). This receptor works by binding to hormone regulating parts of DNA in a cell’s nucleus affecting gene expression… and it is the microbiome which activates FRX by metabolizing of primary bile acids  to secondary bile acids.[6]

All in all much more research into fecal microbial transplants must be undertaken to satisfy safety and ethical demands of the public but it is a promising technique with life changing potential.


[1] NHS Foundation Trust. (n.d.). Faecal microbiota (stool) transplantation (FMT). [online] Available at:

Click to access fmt.pdf

[Accessed 15 Jul. 2019].

[2] Research Gate. (2012). Should We Standardize the 1,700-Year-Old Fecal Microbiota Transplantation?. [online] Available at: https://www.researchgate.net/publication/233537625_Should_We_Standardize_the_1700-Year-Old_Fecal_Microbiota_Transplantation [Accessed 15 Jul. 2019].

[3] PMC. (2017). Association between body mass index and Firmicutes/Bacteroidetes ratio in an adult Ukrainian population. [online] Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5440985/ [Accessed 15 Jul. 2019].

[4] NHS. (2016). What is the body mass index (BMI)?. Available at: https://www.nhs.uk/common-health-questions/lifestyle/what-is-the-body-mass-index-bmi/ [Accessed 15 Jul. 2019].

[5] Research gate. (2007). Microbial Ecology: Human gut microbes associated with obesity. Available at: https://www.researchgate.net/publication/6617713_Microbial_Ecology_Human_gut_microbes_associated_with_obesity?enrichId=rgreq-12bd6ba98811af7d0172fb9c544799a1-XXX&enrichSource=Y292ZXJQYWdlOzY2MTc3MTM7QVM6MTYzMzU3Njc2MDIzODA5QDE0MTU5NTg5MTM1ODc%3D&el=1_x_2&_esc=publicationCoverPdf [Accessed 15 Jul. 2019].

[6] Wikipedia. (n.d.). Farnesoid X receptor. [online] Available at: https://en.wikipedia.org/wiki/Farnesoid_X_receptor [Accessed 15 Jul. 2019].

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