Chapter 39 OBESITY AND ABNORMAL LIVER FUNCTION TESTS
INTRODUCTION
Fatty liver or steatosis refers to the accumulation of fat within the liver. The fatty liver disorders are the most common cause of disturbances of liver function tests in the Western world. While there are several causes of fatty liver, including that of excessive consumption of alcohol (see Chapter 40), the commonest cause is that of insulin resistance usually (but not always) associated with one or a combination of obesity, hyperlipidaemia and/or hyperglycaemia. Non-alcoholic fatty liver disease (NAFLD) is the term used to describe steatosis unrelated to excessive alcohol consumption. NAFLD is a form of metabolic liver disease nearly always associated with insulin resistance and very often with the metabolic, or insulin resistance (IR), syndrome.
Risk factors
NAFLD is associated with central adiposity, obesity, hyperlipidaemia (particularly hypertriglyceridaemia, insulin resistance, the metabolic syndrome and type 2 diabetes—all conditions associated with insulin resistance (see Table 39.1). In addition, NAFLD is associated with rapid weight loss, particularly that observed after jejunoileal bypass surgery (Table 39.2).
Natural history and prognosis
Obesity and fatty liver disorders have been associated with the development of hepatocellular carcinoma, however the exact risk is not known. In a high proportion of patients with cryptogenic cirrhosis, the cirrhosis appears to be related to ‘burnt out’ NASH. That is, these patients fulfil the clinical profile of a patient with an underlying clinical profile of insulin resistance.