Fructose is a Metabolic and Inflammatory Pathogenic Factor in Metabolic Dysfunction-associated Steatohepatitis (MASH)

Inclusion Criteria: * Able and willing to give written informed consent * Age 45-65 at consent * HbA1c \< 48 mmol/mol * Overweight and stage I obesity using BMI thresholds adjusted for ethnicity: * 23.0kg/m2 - 32.4kg/m2 in South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean populations * 25kg/m2 - 34.9kg/m2 in White populations MASH Patients: Clinical diagnosis of MASH and F2 - F3 fibrosis: Either: Liver biopsy within 12 months of baseline Or: • History of histologically-diagnosed MASH with current evidence of fatty liver, AST\>20 and Fibroscan CAP≥248 dB/m and stiffness 9.5kPa -14kPa Or: • FAST score \>0.67 Patients with steatosis: • defined by Fibroscan CAP≥248dB/m and stiffness \<7.9kPa. Healthy controls: • defined by Fibroscan CAP\<248dB/m and stiffness \<7.9kPa. Exclusion Criteria: * Unwilling or unable to give consent * Age \<45 or \>65 * Any form of diabetes mellitus * Currently pregnant * Known fructose intolerance or food allergy * Diagnosis of cirrhosis or Fibroscan stiffness \>14kPa * Current Child-Pugh B/C or episode of decompensation in last year * Non-MASLD liver disease known to participant (including viral hepatitis, auto-immune hepatitis, primary sclerosing cholangitis, primary biliary cholangitis, haemochromatosis, sarcoidosis, cystic fibrosis, sickle cell disease) * Regular alcohol intake \> 14 units a week for females and \>21 units a week for males (participant-reported) * Smoking, vaping or use of nicotine-containing products within the last month * Taking prohibited medication: * Probiotic or antibiotic use within last 4 weeks (Note: participants will be considered eligible if they have undergone a 4-week washout from probiotics or 4-weeks after discontinuing antibiotic use) * any oral steroids within the last 6 weeks * current, or within 3 months, use of immunosuppressive medication * Amiodarone, nitrofurantoin, or anti-fungals within 3 months * Use of anti-obesity medication - orlistat or GLP-1 receptor agonist-containing treatments within 6 months * Use of vitamin E, pioglitazone or other medication for MASH including current or within 3 months enrolment in clinical trial unless documented to have been on placebo * History of malignancy (except basal cell carcinoma), or medication for malignancy within the last 2 years * Any major organ transplant (excluding corneal or hair) * Clinical diagnosis of chronic kidney disease 3 or above, or of heart failure (NYHA 3 or 4) * COPD requiring home oxygen * Known eating disorder (e.g. anorexia nervosa) or severe mental illness (e.g. schizophrenia) * Investigator opinion that study is unsuitable for patient