On this page
NAFLD / MASLD
NAFLD/MASLD affects a significant portion of the adult population in the UK and globally. It is often linked to metabolic risk factors like obesity and type 2 diabetes, and can progress to more severe liver conditions in some individuals.
Overview
Non-alcoholic fatty liver disease (NAFLD), now increasingly referred to as metabolic dysfunction-associated steatotic liver disease (MASLD), is a very common condition affecting the liver. It occurs when too much fat accumulates in the liver cells, not due to heavy alcohol consumption [PMID:36573881]. This condition ranges from simple fatty liver (steatosis), which generally causes little to no harm, to more aggressive forms that can lead to liver inflammation and damage.
MASLD is closely associated with metabolic risk factors such as obesity, type 2 diabetes, high cholesterol, and high blood pressure. Because of its strong link to these factors, it is often considered the liver manifestation of metabolic syndrome. While often mild, MASLD can progress to more serious liver conditions over time, potentially leading to significant health issues [PMID:34739506].
Symptoms & clinical features
Many people with MASLD experience no symptoms, especially in the early stages, and the condition may only be discovered incidentally during tests for other health issues. When symptoms do occur, they are often vague and non-specific. These can include a dull ache or discomfort in the upper right side of the abdomen, persistent tiredness, and a general feeling of being unwell.
As the condition progresses to more advanced stages, such as metabolic dysfunction-associated steatohepatitis (MASH) - previously known as non-alcoholic steatohepatitis (NASH) - and then to cirrhosis (severe scarring of the liver), more noticeable symptoms may appear. These can include yellowing of the skin and eyes (jaundice), swelling in the legs and ankles, fluid build-up in the abdomen (ascites), dark urine, and itchy skin. However, these severe symptoms indicate significant liver damage.
Video: Genetics 101
Affected organs
The primary organ affected by MASLD is the liver. The accumulation of fat in liver cells can lead to inflammation and damage over time. If this inflammation persists, it can cause the formation of scar tissue within the liver, a process known as fibrosis.
In advanced stages, extensive fibrosis can lead to cirrhosis, where the liver becomes severely scarred and loses its ability to function properly. Cirrhosis can eventually result in liver failure, a life-threatening condition. MASLD is also closely linked with metabolic syndrome, which affects multiple body systems, including the cardiovascular system, increasing the risk of heart disease and stroke.
Risks & severity
MASLD is a spectrum disorder, meaning its severity can vary significantly among individuals. The most common form, simple fatty liver, is generally considered benign. However, for some individuals, the condition can progress to MASH, characterised by inflammation and liver cell damage, which carries a higher risk of developing fibrosis and eventually cirrhosis [PMID:34739506]. Cirrhosis is a serious condition that can lead to liver failure and an increased risk of liver cancer.
The exact prevalence of MASLD is not well established, but it is estimated to affect around 25% of adults globally. The risk of progression from simple fatty liver to MASH and then to cirrhosis varies, but factors such as continued obesity, uncontrolled diabetes, and genetic predispositions can influence this progression. While MASLD can affect individuals of any age, it is more commonly seen in middle-aged and older adults, though it is increasingly being diagnosed in children and adolescents.
Genetic causes
MASLD is considered a complex or polygenic condition, meaning it is influenced by a combination of multiple genetic factors and environmental elements. While lifestyle choices, such as diet and exercise, play a significant role, certain genetic variations can increase an individual's susceptibility to developing MASLD and influence its progression [PMID:36573881].
Several genes have been identified that contribute to the risk of MASLD. These include variations in the PNPLA3 (patatin like phospholipase domain containing 3), TM6SF2 (transmembrane 6 superfamily member 2), and HSD17B13 (hydroxysteroid 17-beta dehydrogenase 13) genes. For example, the PNPLA3 gene is involved in lipid metabolism within the liver, and certain variants are associated with increased fat accumulation and inflammation [PMID:34739506]. Similarly, variations in TM6SF2 and HSD17B13 have been linked to an elevated risk of MASLD and more advanced forms of liver disease.
Inheritance pattern
MASLD typically follows a polygenic or complex inheritance pattern. This means that the condition does not result from a change in a single gene, but rather from the combined effects of multiple genetic variations acting together with environmental and lifestyle factors. Therefore, it is not inherited in a simple dominant or recessive manner.
If one family member has MASLD, other family members may have an increased risk, but this is due to a combination of shared genetic predispositions and similar lifestyle factors. There is no simple way to predict who will develop the condition based solely on family history, as many factors contribute to its development and severity.
Diagnosis & testing
Diagnosing MASLD often begins with a suspected clinical picture, especially in individuals with metabolic risk factors. Initial blood tests may reveal elevated liver enzymes, which can indicate liver inflammation. Imaging techniques such as ultrasound, CT scans, or MRI scans can help to identify fat in the liver.
To confirm the diagnosis and assess the severity, particularly the presence of inflammation and fibrosis, a liver biopsy might be performed, though less invasive methods are increasingly used. In the UK, diagnosis and management are typically handled through primary care, with referrals to gastroenterology or hepatology specialists if the condition is thought to be progressive or severe. Genetic testing is not routinely used for MASLD diagnosis in the NHS, but research into genetic risk factors is ongoing. The NHS Genomic Medicine Service may use R-codes for specific genetic tests in certain research or highly specialised contexts, though not for routine MASLD diagnosis.
Management & lifestyle
Management of MASLD primarily focuses on addressing the underlying metabolic risk factors and promoting liver health. Lifestyle modifications are the cornerstone of treatment and include achieving and maintaining a healthy weight, adopting a balanced diet, and engaging in regular physical activity. Weight loss, even modest amounts, can significantly reduce fat in the liver and improve liver inflammation.
Managing co-existing conditions such as type 2 diabetes, high cholesterol, and high blood pressure is also crucial. This may involve medication as prescribed by a healthcare professional. There are currently no specific medications approved solely for MASLD, but medications used to manage associated metabolic conditions can have beneficial effects on the liver. Regular monitoring of liver function through blood tests and imaging may be recommended by your GP or specialist, particularly if there is evidence of liver damage or progression.
UK care pathway
In the UK, the care pathway for MASLD typically starts with your General Practitioner (GP). If MASLD is suspected or diagnosed, your GP will usually advise on lifestyle changes and may monitor your liver function. If there are signs of more advanced liver disease, or if you have significant co-existing metabolic conditions, your GP may refer you to a specialist service, such as a gastroenterologist or hepatologist within the NHS.
Genetic counselling is not routinely offered for MASLD unless there is a very unusual presentation or a strong family history suggesting a specific monogenic cause (which is rare). However, genetic counsellors can provide support and information regarding complex genetic conditions and their inheritance patterns should a genetic link be identified or suspected in an atypical case. While specific R-codes for routine MASLD genetic testing are not currently part of the NHS Genomic Medicine Service test directory, research into the genetic aspects of liver disease continues.
Frequently asked questions
What is the difference between NAFLD and MASLD?
NAFLD (Non-alcoholic fatty liver disease) was the original term for fat in the liver not caused by alcohol. MASLD (Metabolic dysfunction-associated steatotic liver disease) is a newer term introduced to better reflect the strong link between fatty liver and metabolic risk factors like obesity and diabetes. They refer to the same condition.
Can MASLD be reversed?
In its early stages, MASLD can often be improved or even reversed through significant lifestyle changes, particularly weight loss, a healthy diet, and regular exercise. If the disease has progressed to significant scarring (cirrhosis), reversal is less likely, but progression can often be slowed.
Is MASLD a genetic condition?
MASLD is a complex condition influenced by both genetic and environmental factors. While certain genetic variations can increase your risk, it's not inherited in a simple, predictable way like some other genetic conditions. Lifestyle choices play a very significant role.
What lifestyle changes are most important for MASLD?
Key lifestyle changes include achieving and maintaining a healthy weight, especially reducing abdominal fat. Adopting a balanced diet, limiting processed foods, sugary drinks, and unhealthy fats, and engaging in regular physical activity are also crucial for managing MASLD.
Do I need genetic testing for MASLD?
Genetic testing is not routinely used for diagnosing or managing MASLD in the NHS. The diagnosis typically relies on blood tests, imaging, and sometimes a liver biopsy. Genetic research is ongoing, but for most people, lifestyle and metabolic factors are the primary focus.
References
- Zafer M, Tavaglione F, Romero-Gómez M. Review Article: GLP-1 Receptor Agonists and Glucagon/GIP/GLP-1 Receptor Dual or Triple Agonists-Mechanism of Action and Emerging Therapeutic Landscape in MASLD. Alimentary pharmacology & therapeutics. 2025. PMID: 40364529
- Stroes AR, Vos M, Benninga MA. Pediatric MASLD: current understanding and practical approach. European journal of pediatrics. 2024. PMID: 39560782
- Younossi ZM, Golabi P, Price JK. The Global Epidemiology of Nonalcoholic Fatty Liver Disease and Nonalcoholic Steatohepatitis Among Patients With Type 2 Diabetes. Clinical gastroenterology and hepatology : the official clinical practice journal of the American Gastroenterological Association. 2024. PMID: 38521116
- Ciardullo S, Muraca E, Vergani M. Advancements in pharmacological treatment of NAFLD/MASLD: a focus on metabolic and liver-targeted interventions. Gastroenterology report. 2024. PMID: 38681750
- Ezhilarasan D. Mechanism of Semaglutide in MASLD Treatment: Where Is the Master Key? Journal of gastroenterology and hepatology. 2025. PMID: 40538007
- Chen Q, Hu P, Hou X. Association between triglyceride-glucose related indices and mortality among individuals with non-alcoholic fatty liver disease or metabolic dysfunction-associated steatotic liver disease. Cardiovascular diabetology. 2024. PMID: 38965572
- Song R, Li Z, Zhang Y. Comparison of NAFLD, MAFLD and MASLD characteristics and mortality outcomes in United States adults. Liver international : official journal of the International Association for the Study of the Liver. 2024. PMID: 38293788
- Khadilkar V, Shah N, Harish R. Indian Academy of Pediatrics Revised Guidelines on Evaluation, Prevention and Management of Childhood Obesity. Indian pediatrics. 2023. PMID: 38087786