Two people can receive the same diagnosis of fatty liver disease, yet face very different risks. One may develop relatively mild liver changes, while another could progress toward inflammation, scarring and potentially life-threatening complications. The difference may lie not simply in how much fat accumulates in the liver, but in the underlying biological processes driving the disease.
That possibility is attracting attention as researchers investigate whether fatty liver disease should be understood as several distinct biological conditions rather than one disorder affecting everyone in the same way.
The idea could have important consequences for how doctors assess risk, identify patients who need closer monitoring and eventually select treatments. However, there is an important distinction: identifying biological subtypes does not automatically mean medicine has established five separate diseases or developed proven treatments for each one.
What is fatty liver disease, and why does it matter?
Fatty liver disease occurs when excess fat accumulates in liver cells. The condition is now commonly discussed under the name metabolic dysfunction-associated steatotic liver disease, or MASLD, when it occurs alongside at least one cardiometabolic risk factor and other causes have been considered.
MASLD is a major global health concern. Research published in Communications Health notes that the condition affects roughly 32% of the global population, although estimates vary according to the population studied and the diagnostic criteria used.
In its earlier stages, the condition may cause few noticeable symptoms. Some people discover it during an ultrasound, blood test or medical investigation for an unrelated problem. Others may have metabolic risk factors for years without knowing that their liver is accumulating fat.
For many patients, fatty liver does not progress to severe liver damage. In others, however, fat accumulation can accompany inflammation and liver-cell injury, a condition known as metabolic dysfunction-associated steatohepatitis, or MASH. Continued injury can lead to fibrosis, in which scar tissue develops in the liver, and eventually cirrhosis in advanced cases.
The challenge is that the amount of fat in the liver alone does not tell doctors the entire story. Two patients with similar findings may have different combinations of genetic susceptibility, insulin resistance, cholesterol abnormalities and other health conditions.
That variation is one reason scientists are investigating whether a single diagnosis conceals several biologically distinct patterns.
Scientists identify five distinct biological subgroups
A recent study indexed in PubMed investigated the diversity of MASLD by analyzing clinical and genetic information from linked health-record and genomic cohorts. Using a statistical method called latent class analysis, the researchers identified five subgroups with different genetic characteristics, clinical profiles and risks of disease progression. The broad pattern was also observed in an independent cohort.
This is an important distinction: the researchers identified five subgroups within an existing disease classification. They did not establish that fatty liver disease has officially become five separate diseases, nor did they demonstrate that every patient can already be assigned to a subtype in routine clinical practice.
The findings nevertheless suggest that the mechanisms behind fatty liver disease may differ substantially between patients.
Some of the profiles identified in the study illustrate how complicated the condition can be.
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A cardiorenal profile: One subgroup, more common among men, was associated with a substantial burden of cardiometabolic conditions and kidney-related risk.
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An obesity-associated profile: Another subgroup, more common among women, was characterized by obesity, mood disorders and high rates of conditions including type 2 diabetes and sleep apnea.
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A genetically influenced profile: One subgroup had comparatively fewer metabolic complications and a lower incidence of ischemic heart disease, yet experienced the highest rate of liver transplantation in the study. The researchers suggested that the combination of genetic risk factors could help explain this apparently contradictory outcome.
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A higher-risk MASH profile: Another subgroup was associated with increased risk of advanced liver fibrosis and acute kidney failure.
These descriptions are examples of findings reported by the researchers, not a complete clinical classification for diagnosing individual patients. The available study summary does not provide enough detail to describe every characteristic of all five groups with equal confidence.
The broader message is striking: a patient whose liver disease appears relatively uncomplicated from a metabolic perspective may still face significant liver-related risks, while another patient may have a greater burden of diabetes, obesity or cardiovascular complications.
A single label may not fully capture those differences.
Why inflammation, metabolism and genetics may change the outcome
The liver plays a central role in processing fats, regulating blood sugar, storing energy and removing waste products from the bloodstream. When these processes become disrupted, excess fat can accumulate inside liver cells.
Insulin resistance is one important contributor. When the body’s cells respond less effectively to insulin, the liver may receive more fatty acids and produce more fat than it can comfortably manage. This can happen in people with obesity or type 2 diabetes, but it is not limited to them.
Genetics adds another layer of complexity. Certain genetic variants can affect how the liver stores, processes or exports fat. Their effects may differ from those of the metabolic conditions commonly associated with MASLD.
Inflammation also matters. In some patients, excess fat is accompanied by cellular stress, inflammatory responses and liver-cell injury. Over time, repeated injury can activate cells that produce scar tissue, increasing the risk of fibrosis.
These processes do not necessarily occur at the same rate in every person. Nor does the presence of fat automatically mean that severe inflammation or cirrhosis will develop.
The five-subgroup findings support the idea that researchers should look beyond a single measurement of liver fat and investigate the biological factors that influence a patient’s long-term outcome. However, the study does not establish that each subgroup has one unique mechanism or that inflammation alone determines which category a patient belongs to.
Could this lead to personalized treatment?
The long-term possibility is that doctors could eventually use a combination of clinical information, genetic markers and blood-based tests to identify which patients are most likely to develop serious complications.
For example, a patient whose profile suggests a greater risk of advanced fibrosis might benefit from closer assessment of liver scarring. Someone whose risk is dominated by diabetes, obesity or cardiovascular disease may need particular attention to those conditions alongside liver care.
That does not mean patients should wait for subtype testing before seeking treatment.
Lifestyle changes remain important for many people with MASLD. Appropriate weight management, regular physical activity, a balanced diet and effective control of blood sugar, cholesterol and blood pressure can help reduce metabolic risks. Treatment decisions should be individualized with a qualified healthcare professional.
Medication is also becoming an increasingly important part of care for selected patients. Research published in Nature Reviews Gastroenterology & Hepatology describes advances in drug treatment for MASH, including regulatory approvals of resmetirom and semaglutide in the United States for relevant patient groups. These medicines are not appropriate for everyone with fatty liver disease, and their use depends on clinical circumstances and local approvals.
Researchers are also investigating whether molecular tests can distinguish different forms of the disease without requiring an invasive liver biopsy. In a separate study published on October 17, 2026, researchers in India examined blood lipid patterns in 99 participants and identified candidate lipid signatures that distinguished healthy individuals from people with MASLD and differentiated MASLD without steatohepatitis from MASH.
That study was small and exploratory. Its results need independent validation in larger and more diverse populations before the proposed signatures can be considered reliable routine diagnostic tests. It did not establish the same five-subgroup classification.
What scientists still need to prove
Identifying disease subgroups is an important research step, but it does not automatically improve patient outcomes.
Researchers must establish whether the five profiles can be reproduced consistently across populations with different genetic backgrounds, lifestyles and healthcare access. They must also determine whether the groups predict future complications accurately enough to change medical decisions.
An additional challenge is that people can have several overlapping risk factors. A patient may have insulin resistance, high cholesterol, genetic susceptibility and sleep apnea at the same time. Any useful classification system must account for this complexity rather than forcing every patient into an oversimplified category.
The researchers’ findings therefore represent a promising direction for risk assessment and personalized medicine, not a replacement for existing diagnostic methods.
For patients, the practical message remains straightforward: fatty liver disease should not be dismissed simply because it causes no obvious symptoms. People with relevant risk factors should discuss appropriate screening and assessment with their healthcare professional, particularly if they have diabetes or other metabolic conditions.
The future of fatty liver diagnosis
The idea that fatty liver disease may consist of several biological subgroups challenges the assumption that everyone with the diagnosis faces the same risks or needs precisely the same approach to care.
Scientists are beginning to map how genetics, metabolic health and other biological processes interact to influence the disease. If these patterns can be validated and translated into reliable clinical tools, doctors may eventually be able to identify high-risk patients earlier and tailor monitoring and treatment more effectively.
For now, the discovery is a reminder that a diagnosis is often the beginning of understanding a disease, not the end of it. The liver may look similar in two patients, but the biological processes shaping their futures can be very different.
