In the recent years, research on brown adipose tissue (BAT) revealed that larger amounts as well as higher activity thereof are associated with a favourable metabolic phenotype. Longitudinal studies which applied recurrent cooling sessions demonstrated a high plasticity of BAT which significantly increased in size and activity during these studies. These changes were accompanied by improvements in body fat mass as well as insulin sensitivity. Non-alcoholic fatty liver disease (NAFLD) is estimated to advance to the primary cause of liver cirrhosis and hepatocellular carcinoma in the following years. Besides predisposing genetic and possibly nutritional factors, the insulin resistance syndrome and obesity are the main factors contributing to this excessive hepatic lipid accumulation.

The aim of this study is to investigate whether BAT recruitment via cold-acclimation results in decreased hepatic lipid content in overweight/obese patients with NAFLD.

Inclusion Criteria:

• body mass index 28 - 40 kg/m^2
• hepatic lipid content > 10 %

Exclusion Criteria:

• endocrine disease, except treated hypo-/hyperthyroidism and hypertriglyceridemia (<500 mg/dl) and untreated type II diabetes mellitus (fasting glucose < 140 mg/dl)
• use of beta-blockers, alpha-blockers and rilmenidine
• chronic kidney disease
• inflammatory bowel disease
• active malignant disease
• autoimmune disease
• chronic alcohol abuse or alcohol consumption greater than 30g/d for men or 20 g/d for women
• transferrin saturation > 40%
• serum alpha-1 antitrypsin < 90 mg/dl
• serum ceruloplasmin < 20 mg/dl
• positive serology for autoimmune hepatitis
• positive hepatitis serology
• liver cirrhosis
• portal hypertension
• pregnancy
• contraindications for magnetic resonance imaging