This is a randomised controlled study of patients with Non-Alcoholic Fatty Liver Disease (NAFLD).

Patients will be trained according to the 10 rules of a healthy nutrition according to the German Association for Nutrition (DGE).

One arm will undergo Time-Restricted Feeding (TRF) for 12 weeks. The control arm is not subject to any time restrictions concerning eating.

It will be investigated whether TRF improves insulin sensitivity, impacts on metabolic inflammation and reduces liver steatosis.

Patients are recruited in the Liver Outpatient Clinic of the University Medical Center of Mainz.

About 100 patients will be enrolled in this pilot study. Inclusions criteria are exclusions of known causes of liver injury, Body Mass Index (BMI) > 25 kg/m^2, severe steatosis according to CAP ≥ 300 dB/m and absence of advanced fibrosis according to liver stiffness < 13 kPa.

Following the written consent, all patients will be trained to undertake a 2-week lead-in period of DGE.

Beginning in week 3 (Visit 2), an interventional group and a control group are generated through randomisation. The interventional group is instructed to follow TRF, whereas the control group is not subject to any time restrictions. Both arms will be accompanied for a duration of 12 weeks.TRF diet is based on temporal food consumption between 8:00 a.m. and 16:00 p.m., thus a 16 hour lasting period. After 10 weeks from the completion of the experimental phase (wash-out period), there will be the "end of follow up" visit.

The whole duration of the study is 24 weeks (2 weeks lead-in, 12 weeks intervention and 10 weeks post-intervention investigation).

Transient elastography (Fibroscan) is conducted at the screening visit, randomization visit, and at weeks 8, end of treatment visit and end of study visit. Spleen stiffness measurement is performed at randomization visit, week 8 and end of treatment visit. There will be 5 visits at the study center (screening, randomization, week 8, end of treatment and end of study) and 2 phone visits (week 6 and week 12). At each visit clinical events, body weight and standard laboratory parameters, identification of the CAP and stiffness values will be collected. Participants will fill in questionnaires capturing quality of life. At randomization visit and end of treatment visit, an OGTT will be performed to assess insulin sensitivity.

Adverse events will be recorded. Phone visits are used to survey the safety of patients.

Non-adherence to TRF for 2 days per week (20% of the total study period) has been selected as cut off to define treatment failure at per-protocol analysis.

Patients with steady medication during the last 3 months. A diabetes mellitus must not be decompensated (HbA1c <6.5%). Patients with advanced fibrosis - defined about the non-invasive Fibroscan-procedure (Fibroscan >13 kPa) - will not be included.

Complete inclusion criteria:

1. Age between 18 and 75 years
2. Body Mass Index (BMI) > 25 kg/m2
3. Grade 3 steatosis evaluated by with CAP ≥ 300 dB/m and exclusion of known causes of liver steatosis
4. Liver elastography < 13 kPa
5. Capability to understand the study and the individual consequences of participation
6. Signed and dated declaration of agreement in the forefront of the study

Complete exclusion criteria:

1. Liver cirrhosis
2. Hepatocellular carcinoma or non-curative treated carcinoma
3. Alcohol consumption >20g (female) und >30 g (male)/day
4. Other causes of chronic liver disease (HBV, HCV, HDV, HEV, HIV), autoimmune diseases or chronic cholestatic liver disease, hereditary haemochromatosis, Wilson disease, α-1-Antitrypsin deficiency
5. Medications which cause liver disease or secondary NAFLD (e. g. Tamoxifen, systemic Corticosteroids, Methotrexate, Tetracycline, Estrogens, Valproic acid)
6. Changes in body weight > 5% in the last 6 months
7. Statins and/ or other fat-reducer medications if not taken in steady dosage during at least 4 weeks
8. Uncontrolled diabetes type 2 defined as HbA1c value > 9.0% or insulin depending type 2 diabetes
9. Pregnancy
10. Immunologic or inflammatory disease (e. h. systemic lupus erythematodes)
11. Patients after organ transplantations
12. Missing or lacking consent capability

The transfer of data to third parties including publication will be exclusively in form of double pseudo-anonymized data, i.e. cannot be assigned to a person.