The purpose of this study is to learn more about how the body stores fat in and around organs (for example in the liver) and why this affects some people's health more than others. Understanding this may lead to better treatments for diseases such as diabetes and cardiovascular disease.

The purpose of this study is to determine the specific cellular and organ system metabolic and immunologic alterations that are associated with insulin resistance and inflammation in order to identify putative mechanisms and novel bio-markers involved in the pathogenesis and progression of inflammatory and cardiometabolic diseases.

Inclusion Criteria:

Lean, metabolically healthy group - Body mass index (BMI) 18.5-24.9 kg/m2, HbA1C ≤5.6%, fasting plasma glucose concentration <100 mg/dl, 2-h OGTT plasma glucose concentration <140 mg/dl and intrahepatic triglyceride (IHTG) content ≤5%.

Obese, metabolically healthy group - BMI ≥30 kg/m2, HHbA1C ≤5.6%, fasting plasma glucose concentration <100 mg/dl, 2-h OGTT plasma glucose concentration <140 mg/dl and intrahepatic triglyceride (IHTG) content ≤5%.

Obese, metabolically healthy group - BMI ≥30 kg/m2, IHTG content ≥5.6% and HbA1C ≥5.7% or fasting plasma glucose concentration ≥100 mg/dl or 2-h OGTT plasma glucose concentration ≥140 mg/dl.

Lean, scheduled for inguinal hernia, hysterectomy or myomectomy surgery - BMI 18.5-24.9 kg/m2, HbA1C ≤5.6%, fasting plasma glucose concentration <100 mg/dl, 2-h OGTT plasma glucose concentration <140 mg/dl and IHTG content ≤5%.

Obese, scheduled for bariatric and gallbladder surgery - BMI ≥35.0kg/m2

Exclusion Criteria:

• active or previous history of liver diseases other than NAFLD
• history of alcohol abuse
• currently consuming ≥20 g alcohol/day
• severe hypertriglyceridemia (>300 mg/dL)
• smoke tobacco
• cancer diagnosis within the previous 5 years
• medications that might confound the study results
• pregnancy or lactation
• exercise >2 h/week