Long underestimated in France, MASH (formerly NASH) or “fatty liver disease” today affects between 500,000 and 900,000 people. This metabolic dysregulation causes chronic inflammation of the liver which can progress to cirrhosis or cancer.
Long localized in the United States and therefore little known and underestimated in France, NASH (or MASH) is increasingly common there. It would concern between 500,000 to 900,000 French people. It corresponds to “fatty liver” disease which can develop into cirrhosis or even cancer. Lack of exercise, sedentary lifestyle, diet rich in sugars would promote the appearance of NASH. How to detect it? What are the symptoms? What are the risk factors? How to treat it? Interview with Professor Patrick Marcellin, hepatologist at Beaujon hospital and President of the APHC (Association for the improvement of the care of patients with chronic liver diseases).
Should we say NASH or MASH?
NASH is the acronym for Non-Alcoholic SteatoHepatitis in English which means “non-alcoholic steatohepatitis” in French. Since 2023, the global medical community has officially recommended using the term MASH (Metabolic dysfunction-Associated SteatoHepatitis). This change aims to better highlight the metabolic causes of the disease while avoiding the word “alcohol”, which could be perceived as stigmatizing by patients. If the term NASH is still used in everyday language (in this article, we will use the most common term, therefore NASH), it is MASH which now appears in medical records and new health recommendations.
Definition: what is fatty liver disease?
The liver is a storage organ that transforms absorbed sugars into fats: fats necessary for energy and brain function. When there is an abnormal accumulation of fats in the liver cells (called hepatocytes), it is called steatosis. “This steatosis can become pathological when it is excessive and progressive, that is to say when there is an excess of fat, there are hepatic complications and it is associated with inflammation of the liver: this is when we speak of NASH“, explains the hepatologist. NASH is therefore a disease characterized by an accumulation of fat in the cells of the liver, associated with inflammation of this organ. Several studies have shown that the numbers of cirrhosis, cancers and liver transplants have been significantly increasing in recent years, “which is obviously linked to the increasing number of NASH“, specifies the specialist.
What are the symptoms of NASH?
“There is no no specific symptoms linked to excessive steatosis. Some people therefore suffer from NASH disease without presenting no alarming signs or particular physical manifestations“, would like to clarify Professor Marcellin. The whole difficulty is therefore to be able to detect NASH. Statistically, this disease mainly concerns men over 50but also the women after menopause. But in recent years, NASH has also been observed in increasingly younger patients who have:
- a overweight,
- A “American” diet (soda, lots of carbohydrates…) or poorly balanced
- or who present certain risk factors such as cholesterolof the triglycerides…
What are the risk factors for NASH?
This disease can affect anyone, even if there are associated risk factors. “A person who is overweight – even slightly – from diabetes, cholesterol, triglycerides, or high blood pressurehas a greater risk of developing NASH and must therefore be particularly vigilant“, warns the hepatologist. At the moment, we do not know very well the mechanisms responsible for inflammation or fibrosis, however, NASH could be linked to a genetic factor: it is now well established that approximately 10 to 15% of patients with MASH are not overweight (this is “Lean MASH”). The risk is linked to visceral fat (around the organs) and not only to BMI. Even a person A thin-looking person may be affected if their diet is too rich in processed sugars or if they have a genetic predisposition.
What causes NASH?
It is difficult to determine the precise causes of NASH. However, it seems that lack of exercise, sedentary lifestyle, or a diet rich in ultra-processed foods and sugars would promote the appearance of this pathology. In question: “our current dietary lifestyle (consumption of junk food, fast food, industrial products, on-the-go lunches… as well as a sitting position and a sedentary lifestyle at work) means that we absorb more, or even too much, sugars which can accumulate in the liver“, argues the expert. And you should know that sugar is linked to an addiction phenomenon, especially with the excitement of light or “zero” products which, as they contain false sugars and sweetenersdo not alert the satiety centers of the brain as “real sugar” does, stimulate the appetite and encourage us to consume even more sugar. And like “the more sugars we swallow, the more we want to consume them“, steatosis is becoming more and more common. In addition, many foods that we consume daily do not initially seem sweet, but contain a lot of it. These include industrial products, fruit juices, sauces, sandwich breads, dietetic products and even prepared vegetable pans….
Since there are no visible symptoms, diagnosis relies on a multi-step screening strategy, aimed at identifying inflammation and, more importantly, the degree of fibrosis (scarring) of the liver.
► Step 1: The FIB-4 score (First sort). Today, the classic blood test is no longer limited to the observation of transaminases. “If a high level of transaminases remains an alarm signal, it can be normal even in cases of advanced disease“, warns the hepatologist. Doctors now primarily use the FIB-4 score. This simple calculation, based on age, transaminase level and platelet level, makes it possible to very quickly assess the risk of fibrosis in community medicine.
► Step 2: Specialized biomarkers. If the FIB-4 score is suspicious, second-line, more in-depth blood tests are performed. Tools like the ELF (Enhanced Liver Fibrosis) test or the FibroMeter have become standards in 2026. They measure biological markers directly linked to the degradation of the liver matrix, offering much greater precision than the tests of the past to confirm the presence of MASH.
► Step 3: Imaging and elastometry. Ultrasound allows you to visualize the fat, but it is elastometry (performed using a FibroScan®) which is the key examination. “It makes it possible to quantify steatosis but above all to measure the ‘hardness’ of the liver to determine the exact stage of fibrosis.“, specifies the expert. Thanks to the combined performance of these blood tests and FibroScan®, liver biopsy (sampling of a liver fragment) has now become exceptional and is only reserved for the most complex cases.
Taken in time, at the precirrhotic stage, the disease is reversible: a balanced diet and regular physical activity remain the pillars to stop the process. However, the therapeutic landscape has reached a historic milestone: specific drug treatments are now available or in the final stages of authorization. We finally have molecules capable of directly targeting fibrosis and liver inflammation, such as resmetirom (marketed under the name Rezdiffra), the first treatment to have obtained marketing authorization in Europe for patients with significant fibrosis. Other options, such as lanifibranor, are also at the heart of current therapeutic strategies.
The specialist emphasizes, however, that these medications do not replace the fundamentals: “Medical innovation supports the patient’s efforts, but lifestyle changes – reducing processed sugars, limiting saturated fats and increasing physical activity – remain essential to sustainably eliminate liver fat..” He also notes the growing interest in GLP-1 receptor agonists, such as semaglutide or tirzepatide, which, by treating overweight and diabetes, act indirectly but powerfully on liver health.
It is strongly recommended to adopt multidisciplinary care. In addition to the hepatologist and the general practitioner, support from a dietician and, if necessary, an addictologist or psychologist, is essential. Weight loss, even moderate (around 5 to 10%), generally leads to normalization of transaminases and a significant reduction in steatosis and inflammation.
Is NASH reversible?
“Steatosis is reversible : in the absence of medication, a healthy lifestyle and a more balanced diet help reduce the risk of complications“, concludes the specialist.
Thanks to Professor Patrick Marcellin, at the time of publication of the article (2020), hepatologist at Beaujon hospital and President of the APHC (Association for the improvement of the care of patients with chronic liver diseases). Updated with the expertise of Professor Laurent Castera, specialist in liver diseases, international expert in MASH and non-invasive methods for diagnosing hepatic fibrosis (Beaujon Hospital, Paris)
