Fatty Liver Disease (FLD) involves the accumulation of excess fat in liver cells, a condition often asymptomatic in its early stages. Routine blood work is an invaluable tool for detection, as liver enzymes facilitate metabolic processes within the liver. Elevated levels of these enzymes in a blood test signal that the liver may be under stress or experiencing cellular injury. Understanding these elevations in the context of fat accumulation is crucial for maintaining long-term liver health.
The Key Liver Enzymes Measured
Healthcare providers assess several enzymes in a liver function panel. Alanine Aminotransferase (ALT) and Aspartate Aminotransferase (AST) are the primary markers of liver cell injury and are often elevated in fatty liver disease. ALT is found predominantly within hepatocytes, the main liver cells, making its elevation a more specific indicator of liver damage than AST. AST is also abundant in liver cells but is present in other tissues, such as muscle and heart, meaning elevated AST levels can sometimes indicate non-hepatic issues.
Gamma-Glutamyl Transferase (GGT) is concentrated in the liver and bile ducts. An elevated GGT, especially when coupled with high ALT, often suggests liver injury and is a sensitive indicator of fatty liver disease. Alkaline Phosphatase (ALP) is also included, though it is present in bone and intestines, as well as the liver. If ALP is elevated, providers examine GGT levels to confirm the source is the liver or bile ducts. Normal ranges are generally low, with typical upper limits for ALT around 36 to 45 International Units per Liter (IU/L) and AST around 35 IU/L.
Why Enzyme Levels Rise in Fatty Liver Disease
Elevated enzymes result from the excessive buildup of fat (steatosis) within liver cells. This accumulation disrupts normal hepatocyte function and initiates an inflammatory response in the liver tissue. This inflammatory state is known as steatohepatitis. Inflammation compromises the membranes of the liver cells. As the cell wall integrity breaks down, enzymes like ALT and AST, which are normally confined inside the hepatocyte, spill into the bloodstream. Elevated enzyme levels are thus a direct reflection of ongoing liver cell injury caused by the fatty buildup.
Understanding Your Test Results
The degree of elevation and the relationship between enzymes offer important diagnostic clues when reviewing a liver panel. Mildly elevated enzymes, typically less than three times the upper limit of normal, are common in fatty liver disease. Even levels at the higher end of the “normal” range can sometimes be associated with metabolic syndrome and underlying fatty liver.
The ratio of AST to ALT is often used to narrow down the cause of injury. In most cases of fatty liver disease, ALT is higher than AST, resulting in an AST/ALT ratio less than one. Conversely, an AST/ALT ratio significantly greater than two-to-one is more suggestive of alcoholic liver disease or advanced scarring (cirrhosis). Severely elevated levels, ten times the upper limit or more, generally point toward acute liver injury from causes like certain medications or viral hepatitis. Elevated enzymes alone do not diagnose fatty liver disease, and a physician must investigate results to rule out other causes of damage.
Strategies for Reducing Elevated Enzymes
The most effective way to lower elevated liver enzymes caused by fatty liver disease is through targeted lifestyle modifications that address the root cause. Achieving gradual weight loss is the primary strategy, as a reduction of just 7% to 10% of body weight has been shown to improve steatosis, inflammation, and liver fibrosis. It is important that this weight loss is not rapid, as losing weight too quickly can sometimes exacerbate liver injury.
Dietary changes should focus on reducing the intake of refined carbohydrates, added sugars, and saturated fats, which are major contributors to fat accumulation in the liver. Adopting an eating pattern similar to the Mediterranean diet, which emphasizes vegetables, whole grains, lean proteins, and healthy fats like olive oil, helps to reduce fat stored in the liver.
Regular physical activity is another component that can improve liver health, even independent of significant weight loss. Current recommendations suggest aiming for at least 150 minutes of moderate-intensity aerobic exercise each week, which can include brisk walking or resistance training. Avoiding alcohol, even in cases of non-alcoholic fatty liver disease, helps to reduce the overall burden on the liver and supports its recovery. Successfully lowering enzyme levels through these actions is a positive indication that the underlying fatty liver condition is improving.