Fatty Liver Disease (AFLD/NAFLD, MASLD/MetALD)

Moderate Evidence

Overview

Fatty liver disease is a broad term for conditions in which excess fat accumulates in liver cells. The terminology in this field has evolved in recent years. What was historically called nonalcoholic fatty liver disease (NAFLD) is increasingly referred to as metabolic dysfunction–associated steatotic liver disease (MASLD), reflecting its strong relationship to insulin resistance, central adiposity, dyslipidemia, and other features of metabolic dysfunction. Alcohol-related fatty liver disease is often described as alcohol-associated liver disease (ALD/AFLD), and newer nomenclature also includes MetALD, which refers to steatotic liver disease in people who have metabolic risk factors plus alcohol intake above MASLD thresholds but below levels typically used for primary alcohol-associated liver disease. These terms all describe overlapping patterns of liver fat accumulation, but the clinical context matters because risk, prognosis, and management differ.

Fatty liver disease is common worldwide and has become one of the leading causes of chronic liver disease. Research from major liver societies and public health organizations indicates that MASLD/NAFLD affects roughly a quarter of the global adult population, with higher rates among people with obesity, type 2 diabetes, metabolic syndrome, sleep apnea, and polycystic ovary syndrome. Many people have simple steatosis, meaning fat in the liver without major inflammation or scarring. Others develop a more active and potentially harmful form historically called nonalcoholic steatohepatitis (NASH), now often termed MASH when linked to metabolic dysfunction. In MASH, liver fat is accompanied by inflammation and hepatocyte injury, increasing the risk of fibrosis, cirrhosis, liver failure, and hepatocellular carcinoma.

A central challenge is that fatty liver disease is often silent in its early stages. Many cases are detected incidentally through elevated liver enzymes, imaging findings, or evaluation of cardiometabolic risk. Importantly, liver enzyme levels may be normal even when significant fibrosis is present. Because of this, contemporary care places increasing emphasis on risk stratification, especially identifying people with progressive fibrosis, since fibrosis stage is one of the strongest predictors of liver-related outcomes. In addition to liver complications, MASLD is closely associated with cardiovascular disease, which is a major cause of illness and death in this population.

From a broader health perspective, fatty liver disease sits at the intersection of hepatology, endocrinology, nutrition, cardiometabolic medicine, and public health. Conventional medicine focuses on diagnosis, fibrosis assessment, metabolic risk reduction, and in selected cases medications or bariatric interventions. Traditional systems of medicine tend to interpret fatty liver through patterns involving impaired digestion, stagnation, excess, or toxic accumulation, and may use dietary frameworks, botanicals, and lifestyle regulation to support whole-body balance. Across both paradigms, there is growing recognition that fatty liver disease is not a single uniform disorder but a spectrum shaped by metabolism, alcohol exposure, genetics, environment, and inflammatory signaling.

Western Medicine Perspective

In conventional medicine, fatty liver disease is understood as a spectrum of steatotic liver disorders driven by altered fat metabolism, insulin resistance, oxidative stress, inflammation, mitochondrial dysfunction, and, in some cases, alcohol-related injury. MASLD is diagnosed when hepatic steatosis is present along with at least one cardiometabolic risk factor and other major causes of liver disease have been considered. Alcohol-associated disease is assessed separately, while MetALD recognizes a mixed phenotype in which both metabolic dysfunction and alcohol exposure contribute. Diagnostic evaluation commonly includes a history of alcohol use, medication review, viral hepatitis screening when appropriate, liver chemistry tests, metabolic assessment, and imaging such as ultrasound or elastography. Increasingly, noninvasive tools such as FIB-4, transient elastography, and serum fibrosis panels are used to estimate fibrosis risk and identify who may need specialist evaluation.

Research consistently shows that the most clinically important distinction is not simply whether fat is present, but whether there is inflammation and fibrosis progression. Liver biopsy remains the reference standard for distinguishing simple steatosis from steatohepatitis and staging fibrosis, but because biopsy is invasive, modern practice often relies first on validated noninvasive testing. Studies indicate that people with type 2 diabetes, obesity, older age, and multiple metabolic risk factors are more likely to develop advanced fibrosis. Conventional management therefore centers on the broader metabolic picture: body weight, glycemic control, blood pressure, lipids, cardiovascular risk, and alcohol exposure all influence outcomes. In recent years, pharmacologic options for selected patients with MASH and fibrosis have drawn increasing interest, though the evidence base and regulatory landscape continue to evolve.

From an evidence standpoint, lifestyle-related interventions have historically formed the foundation of care, while medications have had more limited and targeted roles. Clinical trials have studied GLP-1 receptor agonists, pioglitazone, vitamin E in selected populations, SGLT2 inhibitors, and newer antifibrotic or metabolic agents, with mixed but growing evidence depending on the endpoint measured. Professional societies generally emphasize that treatment decisions depend on fibrosis stage, diabetes status, cardiovascular risk, and competing liver diagnoses. Importantly, conventional medicine also views fatty liver disease as a multisystem condition; for many patients, prevention of cardiovascular events is as important as preventing cirrhosis.

Eastern & Traditional Perspective

Eastern/Traditional Medicine Perspective

In Traditional Chinese Medicine (TCM), fatty liver disease is not typically framed as a single disease entity but is interpreted through patterns such as dampness accumulation, phlegm, qi stagnation, blood stasis, spleen deficiency, and liver constraint. A person with hepatic steatosis may be understood as having impaired transformation and transportation of սն (food and fluids), leading to internal dampness that congeals into phlegm and obstructs the liver network. Emotional stress, irregular eating patterns, rich foods, and sedentary habits are traditionally seen as aggravating factors. TCM approaches often aim to restore flow, strengthen the spleen, transform dampness, and move blood, using individualized combinations of acupuncture, dietary principles, and classical or modified herbal formulas.

In Ayurveda, liver and metabolic disorders may be interpreted through disturbances in agni (digestive/metabolic fire), accumulation of ama (metabolic residues or toxins), and imbalances in kapha and pitta, particularly when heaviness, sluggish metabolism, and inflammatory features are present together. Classical Ayurvedic thinking often connects liver congestion and fatty accumulation with excess nourishment that is not properly transformed. Management frameworks traditionally emphasize personalized diet, digestive support, routine regulation, movement, and herbs used for liver and metabolic balance, such as preparations involving kutki, guduchi, bhumyamalaki, turmeric, or triphala, depending on the practitioner’s assessment and lineage.

In naturopathic and integrative medicine, fatty liver disease is commonly approached as a manifestation of metabolic overload, chronic inflammation, insulin resistance, and altered gut-liver signaling. This perspective may include attention to sleep, stress physiology, alcohol use, environmental exposures, microbiome-related factors, and nutrient status. Botanicals and nutrients such as milk thistle, berberine, omega-3 fatty acids, curcumin, and coffee-associated polyphenol pathways are frequently discussed in the integrative literature, although evidence quality varies substantially by intervention and endpoint.

The traditional and integrative evidence base is heterogeneous. Some small trials and meta-analyses suggest that certain herbal formulas, acupuncture approaches, or nutraceuticals may improve liver enzymes or imaging markers, but study quality is often limited by small sample size, short duration, variable diagnostic criteria, and inconsistent product standardization. For that reason, traditional medicine perspectives are best understood as complementary frameworks that may offer symptom and lifestyle context, while significant fibrosis, cirrhosis risk, or unclear liver abnormalities generally warrant evaluation within conventional hepatology as well.

How They Relate

Condition / Condition