Metabolism - the basics

  • Metabolism is a general term for the breakdown of food and production of energy within the body. Sugar and fat are sources of energy.
  • Abnormalities in sugar and fat levels and in the processing of fats and sugars may indicate metabolic disorders and can cause physical symptoms.
  • The general term for blood fats is lipids. There are two main types of lipids: cholesterol and triglycerides.
  • There are several types of cholesterol, of which two - LDL (or ‘bad’) and HDL (or ‘good’) - are most important.
  • LDL or low-density lipoprotein is often known as 'bad' cholesterol. High levels of LDL cholesterol increase the risk of heart disease. Antiretroviral therapy has been associated with high LDL and total cholesterol.
  • HDL or high-density lipoprotein is protective against heart disease. Low levels of HDL or ‘good’ cholesterol are a risk factor for heart disease and are frequently found in people taking protease inhibitors. HIV infection itself may cause low HDL levels.
  • Other risk factors also increase the risk of heart disease: smoking, high blood pressure, a family history of heart disease, and age over 45 years. For people on protease inhibitors, it is especially important to monitor levels of ‘bad’ (LDL) cholesterol, which causes most of the damage that leads to heart disease. If you have two or more risk factors, the target level for LDL cholesterol is less than 3.4mm.
  • The target total cholesterol level is 5.2mm or below. The average cholesterol level in the UK is higher than this (around 5.6mm), and a level of 5.9mm or above is high
  • Triglycerides are fats which travel through the bloodstream to be stored in tissues or the liver. The target level is 2.3mm or less, and a level above 4.5mm is considered high.
  • HIV itself causes high triglycerides in advanced disease. Low HDL or ‘good’ cholesterol has also been attributed to HIV infection.
This content was checked for accuracy at the time it was written. It may have been superseded by more recent developments. NAM recommends checking whether this is the most current information when making decisions that may affect your health.