Study population: Patients diagnosed with non-alcoholic or metabolically mediated fatty liver disease (NAFLD/MAFLD), including the inflammatory form (NASH), confirmed by imaging (ultrasound, MRI-PDFF) or histopathological (liver biopsy) methods.
Inclusion criteria:
* Diagnosis of NAFLD/MAFLD or NASH (imaging or histological confirmation of fatty liver disease, e.g., ultrasound, MRI-PDFF, biopsy)
* Age 18-60 years
* Ability to understand the study procedures and provide informed consent.
* Stable clinical condition for at least 3 months prior to study initiation.
Exclusion criteria:
* Lack of fluency in English or Polish
* Significant (structural) limitation of upper and/or lower limb mobility
* Pregnancy or breastfeeding
* Inability to understand instructions
* Shift work
* Participation in any study or research project within the last 3 months
* Participation in an interventional drug study within the last 3 months
* Participants with hepatic steatosis and regular alcohol consumption \> 30 g/day
* Individuals with any concomitant liver disease (viral hepatitis, drug-induced liver injury, metabolic/genetic diseases (e.g., Wilson's disease))
* Anticoagulant/antiplatelet therapy, antithrombotic therapy, immunosuppressive medications, prolonged immunosuppression (e.g., recent cytotoxic chemotherapy, HIV infection with CD4 count \< 240), antibiotics, corticosteroids, valproic acid, amiodarone, tamoxifen within 3 months prior to study enrollment
* Use of medications such as steroids, methotrexate, metformin
* Use of agents such as vitamin E, omega-3 fatty acids, or medications with evidence of an effect on NAFLD (pioglitazone, GLP-1 analogues, dipeptidyl peptidase IV inhibitors, ursodeoxycholic acid)
* Active or previous history of invasive cancer (excluding curatively treated carcinoma in situ \[e.g., cervical\] or benign skin cancer), unless complete remission has been achieved
* Regular use of probiotic or prebiotic supplements within 3 months prior to study enrollment
* Known allergy to probiotics
* History of using an alternative diet within 3 months prior to study enrollment or changing diet during study entry
* Previous surgery (bariatric surgery, gastric or intestinal resection)
* Parenteral nutrition (TPN) within the last 6 months
* Insulin therapy
* Uncontrolled diabetes
* Cardiovascular disease (e.g., uncontrolled blood pressure, coronary artery disease, NYHA class III-IV heart failure, severe arrhythmias, orthostatic intolerance)
* Nervous system disorders
* Cognitive impairment and dementia
* Osteoporosis/osteopenia
* Active thyroid disease
* Cushing's syndrome
* Any implanted battery-powered device (e.g., AICD, pacemaker, cardiac rhythm recorder, cochlear implant)
