The goal of this pilot experimental medicine interventional study is to explore the degree of transferability of the gut microbiome and associated metabolomic changes in patients with non-alcoholic fatty liver disease (NAFLD) and fibrosis who receive faecal microbiota transplant (FMT). The main questions is aims to answer is:

• To what extent is the gut microbiome transferable from donor to recipient in patients with NAFLD with fibrosis who receive FMT?
• What are the dynamics of how the gut microbiome changes over time in these patients?
• To what degree does the recipient metabolome change in association with this?

Participants will receive up to three capsulised FMT preparations prepared from a donor selected rationally based upon their metabolomic characteristics. They will be asked to attend for serial clinical assessments (including FibroScan and MRE/ MRI-PDFF), and will also be asked to provide serial blood, urine and stool samples for assessment of microbiome and metabolome profiling.

Inclusion Criteria:

1. 18-75 years of age.
2. Previously-diagnosed NAFLD, with predicted fibrosis based upon non-invasive assessment with FibroScan (i.e. liver stiffness measurement (LSM) > 8kPa).
3. Raised liver ALT (> 30IU/l for men, > 19IU/l for women) or AST (> 37IU/l for men, > 31IU/l for women) with negative non-invasive liver screen (including negative screen for viral hepatitis, autoimmune liver disease and metabolic liver disease, and normal echocardiogram within two years in the scenario where congestive hepatopathy may be considered).
4. Able to consent for themselves in English.

Exclusion Criteria:

1. Severe or life-threatening food allergy.

2. Pregnant or lactating women; or women trying to conceive.

3. Patients with suspected or confirmed cirrhosis (as assessed by clinical, radiological or histological criteria).

4. Use of particular medications, including:

   1. Systemic antibiotics within the six weeks prior to study enrolment.
   2. Immunosuppression that may influence risks related to FMT (including - but not limited to: use of corticosteroids within eight weeks of intervention; use of cytotoxic chemotherapy; use of azathioprine, tacrolimus, mycophenolate mofetil and/or immunosuppressive biologic therapy, e.g. infliximab).
   3. Use of GLP-1 agonists.

5. Patients not expected to survive the duration of the study's follow-up (six months).

6. Swallowing difficulties that may preclude safe use of FMT capsules, including oral-motor dyscoordination.

7. Alcohol consumption > 20g/ day.

8. Any active cancer (including treatment within the past six months).

9. Active infection at the point of recruitment, including COVID-19 infection.

10. Prior receipt of a liver transplant.

11. BMI < 23 in Asian potential participants and BMI < 25 in Caucasians.

12. Advanced chronic kidney disease (eGFR < 30 ml/min).

13. Chronic intestinal disease, including coeliac disease, cystic fibrosis, inflammatory bowel disease, irritable bowel syndrome, and chronic diarrhoea.

14. Prior bariatric surgery.

15. Patients unable to undergo MRI scans (e.g. due to the individual having metallic implants).

Only anonymised microbiome and metabolome data will be shared with other researchers via open access repositories