Introduction: Currently, Nonalcoholic Fatty Liver Disease (NAFLD) is the most common liver disease in the world. The only approved treatment for it is lifestyle modification and weight loss; however, there is no evidence for patients with normal or low body mass index (BMI).

The aim of this study is to evaluate the efficacy of symbiotic supplementation in NAFLD patients with normal or low BMI.

Methods and analysis: In this randomized, double-blind, placebo-controlled clinical trial protocol, 21 cases and 21 controls will be individually matched based on age and sex. This 42 patients with NAFLD will be supplemented twice daily for 28 wk with either a synbiotic or a placebo capsule. Both groups will be advised to follow an energy balanced diet and physical activity recommendations.

Inclusion Criteria:

• Age of 18 to 70 years
• Body Mass Index (BMI) below 25
• Serum alaninaminotransferase more than 1.5 fold of upper limit of normal range
• Sonographic findings compatible with hepatic steatosis (degree 2 or more)

Exclusion Criteria:

• Diabetes
• Taking any kind of antibiotics two weeks before recruitment
• History of alcohol consumption
• pregnancy or lactation
• Professional athletes
• Other liver disease (viral/etc)
• Use of drugs such as calcium channel blockers, high dose synthetic estrogens, methotrexate , amiodarone, steroids, chloroquine, immunosuppressive drugs, lipid-lowering agents, metformin and vitamin E
• A history of Hypertension, Cardiovascular disease, Pulmonary disease, Renal disease & Celiac disease; Cirrhosis
• History of Upper GI surgery / Prior surgical procedures such as jejunoileal or jejunocolic bypass, gastroplasty
• Following program to lose weight in recent 3 mo
• A history of hypothyroidism or Cushing's syndrome