This study will determine the role of the NK cells before and after bariatric surgery. The investigators selected patients with NAFLD.

A Fibroscan evaluation will be assessed as a new modality to evaluate liver fibrosis.

All morbidly obese patients who are candidates for a bariatric procedure in the investigators institution who has a fatty liver in their routine preoperative US will undergo a fibroscan to assess the degree of liver fibrosis preoperatively in addition to a blood sample that will be withdrawn from those participants to isolate the NK cells and to assess their activities by the assessment of the active form of NK cells (CD107a) using the spectrometry (FACS) analysis.

The investigators will also collect other clinical data including comorbidities (hypertension, diabetes mellitus and hyperlipidemia) in addition to the following routine blood test( complete blood count, creatinine, urea, International normalized ratio, liver function test, HBa1C, cholesterol, HDL, LDL, triglycerides, vitamin D, vitamin B12, potassium, sodium, albumin, bilirubin, C- reactive protein, iron, ferritin and transferrin).

All of the above mentioned tests including the NK cells and the fibroscan will be examined for all participants in 3, 6, 12 months postoperatively.

Inclusion Criteria:

• age from 18-65
• body mass index above 30 with comorbidity or above 35 with or without comorbidity
• evidence of hepatic fibrosis in routine preoperative US

Exclusion Criteria:

• patient with known other liver disease such as autoimmune or alcoholic hepatitis
• patient that take hepatotoxic medication or hormonal treatment
• active alcohol abuse above 20 gram per day
• Drug abuse
• patient refusal
• pregnancy

obese patient with BMI above 30 with comorbidity or BMI above 35 with or without comorbidity, that have evidence of hepatic fibrosis on the routine preoperative US