This article was created with Amy Goss, PhD, Associate Professor of Nutrition Sciences at University of Alabama at Birmingham and Registered Dietitian. This article was edited by Elizabeth Hyska.
Metabolically–dysfunction–associated steatotic liver disease (MASLD) — formerly referred to as nonalcoholic fatty liver disease — is a condition where excess fat builds up in the liver due to metabolic health problems like obesity, diabetes, high blood pressure, or abnormal cholesterol. MASLD has emerged as the most common chronic liver disease worldwide and is a major contributor to heart and metabolic health problems. Its rising prevalence closely parallels global increases in obesity, sedentary behavior, and poor dietary quality, underscoring the central role of lifestyle factors in both disease pathogenesis and management.
Epidemiology and Global Burden of MASLD
Estimates suggest MASLD affects over 30% of the global adult population, making it a significant public health challenge. Prevalence is often higher in males and varies substantially by geographic region and ethnicity. In one study, particularly high prevalence rates were reported in Latin American populations (44%), followed by Middle Eastern and North African populations (36.5%) and Southeast Asian populations (33.8%). These disparities likely reflect differences in genetic susceptibility, dietary patterns, urbanization, and cardiometabolic risk factor burden.
Given its high prevalence and typically silent clinical course, MASLD contributes substantially to downstream complications, including liver fibrosis, cirrhosis, hepatocellular carcinoma, and — critically — cardiovascular disease (CVD), which remains the leading cause of death in this population.
MASLD Definition and Diagnostic Criteria
MASLD is diagnosed when fat makes up at least 5% of the liver, and a person has one of four metabolic risk factors, such as:
- Obesity
- Hypertension
- Dyslipidemia (low HDL cholesterol and/or elevated triglycerides)
- Type 2 diabetes mellitus
This definition emphasizes the metabolic underpinnings of the disease and reinforces the concept that MASLD is not an isolated liver disorder but rather a hepatic manifestation of systemic metabolic dysfunction.
Importance for Patients at Risk or Who Already Have Heart Disease
MASLD and heart disease share common upstream risk factors, including unhealthy dietary patterns, physical inactivity, and cigarette smoking. These lifestyle exposures promote a cascade of adverse biological processes that drive both hepatic and vascular disease.
They also share many of the same underlying problems, including inflammation, insulin resistance, and unhealthy cholesterol patterns. These changes can damage blood vessels and increase the risk of heart attack and stroke. Beyond these well-established pathways, MASLD is also characterized by unhealthy fat stored deep in the abdomen and around organs, which exacerbates metabolic dysfunction. In addition, growing evidence implicates an imbalance in the intestinal microbiota (dysbiosis) in disease progression, which may contribute to increased gut permeability, systemic inflammation, and altered bile acid and lipid metabolism.
Together, these mechanisms help explain why MASLD is strongly associated with early blood vessel damage, changes in heart structure, and increased cardiovascular events.
MASLD Detection and Risk Stratification
MASLD is often detected incidentally through imaging studies performed for other indications. Many people with MASLD have no symptoms, which is why early detection and routine check-ups are important. Ultrasound remains the most commonly used first-line modality due to its accessibility and low cost, although it lacks sensitivity for mild steatosis. Magnetic resonance imaging (MRI) provides greater accuracy and offers the highest sensitivity for quantifying liver fat content.
Assessment of fibrosis risk is essential for prognostication and management. Non-invasive fibrosis scoring tools, such as simple blood-test-based scores like Fibrosis-4 index (FIB-4), are widely used in clinical practice to identify patients at higher risk for advanced fibrosis who may benefit from specialist referral and closer monitoring. FIB-4 can be less reliable in certain age groups, so indeterminate or high results are usually followed by a specialized ultrasound (elastography) or other second-line noninvasive tests.
Lifestyle Intervention as First-Line Therapy
Lifestyle modification remains the cornerstone of MASLD management and is recommended as first-line therapy across all disease stages.
Exercise and Weight Loss
Physical activity plays a central therapeutic role, with benefits extending beyond weight reduction. A 5% reduction in body weight is associated with an approximately 25% decrease in liver fat content and meaningful improvements in metabolic parameters. Weight loss of 7–10% has been shown to reduce liver inflammation and may improve liver scarring, while losses exceeding 10% are associated with the stabilization or reversal of liver scarring in some people. Even modest weight loss can make a meaningful difference.
Both aerobic and resistance exercise training effectively reduce hepatic fat, even in the absence of substantial weight loss. However, resistance training can offer additional advantages by enhancing cardiometabolic health, improving insulin sensitivity, reducing inflammation, and improving heart health, making it a particularly valuable component of comprehensive lifestyle therapy.
Dietary Intervention
Dietary recommendations for MASLD closely resemble the Mediterranean dietary pattern, which has consistently demonstrated benefits for liver fat, insulin resistance, and cardiovascular risk. This approach emphasizes a vegetable-based diet, with:
- Whole grains as primary carbohydrate sources
- Plant-based oils, particularly olive oil, are the primary source of dietary fat
- Nuts and legumes as key protein sources
Emerging evidence also supports the ketogenic diet as an effective short-term strategy for reducing hepatic steatosis, likely through rapid reductions in insulin levels and liver fat, but low-carbohydrate diets like this should only be followed under medical supervision, especially for people with high cholesterol or heart disease.
Alcohol and Smoking
Alcohol consumption should be limited, and alcohol avoidance is recommended in individuals with MASLD to reduce the risk of disease progression, cirrhosis, and hepatocellular carcinoma. Even modest alcohol intake may worsen liver injury, especially in people with advanced liver scarring.
Smoking cessation is strongly recommended, as smoking accelerates fibrosis progression, worsens cardiovascular risk, and contributes to overall morbidity and mortality in MASLD.
Conclusion
MASLD represents a highly prevalent, metabolically driven condition with profound implications for liver and cardiovascular health. Lifestyle changes are the foundation of treatment, although medications may be recommended for some people to help manage obesity, diabetes, or other risk factors. The good news is that MASLD is often reversible, especially in its early stages. Healthy weight loss, regular exercise, improved nutrition, avoiding alcohol, and quitting smoking can significantly reduce liver fat and protect your heart.
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