Does Fatty Liver Affect Your Immune System?

Fatty liver disease and the immune system are closely connected, with excess liver fat disrupting immune regulation and driving chronic, low-grade inflammation throughout the body. The liver is one of the body's primary immune organs, housing specialised cells such as Kupffer cells, natural killer cells, and dendritic cells. When fat accumulates in liver tissue, these cells become dysregulated, affecting both local and systemic immunity. Metabolically associated steatotic liver disease (MASLD), formerly known as NAFLD, is increasingly common in the UK and understanding its immune consequences is essential for effective management and long-term health.

Does fatty liver disease affect your immune system?

Fatty liver disease disrupts the liver's resident immune cells and increases systemic cytokine release, impairing both local and body-wide immune regulation.

Fatty liver disease does affect the immune system, disrupting normal immune regulation and promoting a state of chronic, low-grade inflammation throughout the body. The liver is not simply a metabolic organ; it is one of the body's primary immune organs, housing a large proportion of the body's resident immune cells, including Kupffer cells (the liver's specialised macrophages), natural killer cells, and dendritic cells. When excess fat accumulates in liver tissue, these cells become dysregulated, altering both local and systemic immune responses.

Metabolically associated steatotic liver disease (MASLD), previously known as non-alcoholic fatty liver disease (NAFLD), affects a significant proportion of adults in the UK. Readers should be aware that UK guidance documents, NHS pages, and British Liver Trust materials may still use the older NAFLD and NASH terminology, which corresponds directly to MASLD and metabolic dysfunction-associated steatohepatitis (MASH). In its earlier stages, fat accumulation alone (hepatic steatosis) may cause relatively modest immune disruption. However, as the condition progresses to MASH, immune activation becomes more pronounced and sustained.

The liver's dual role as a filter for gut-derived bacteria and toxins and as a regulator of systemic immunity means that when it is compromised by fat accumulation, the consequences extend well beyond the liver itself. Immune signalling molecules called cytokines are released in greater quantities, affecting organs and tissues throughout the body. Understanding this connection is important for anyone managing fatty liver disease, as immune dysfunction may contribute to a range of associated health conditions.

How does fat build-up in the liver trigger inflammation?

Excess fat causes hepatocytes to release danger signals that activate Kupffer cells, triggering pro-inflammatory cytokines and systemic inflammation via the bloodstream and gut-liver axis.

Fat accumulation in liver cells triggers inflammation through several overlapping processes, of which lipotoxicity is a central one. Excess fatty acids and their metabolites directly damage hepatocytes and activate resident immune cells. When hepatocytes (liver cells) become overloaded with fat, they release danger signals known as damage-associated molecular patterns (DAMPs). These signals are detected by Kupffer cells and other immune sentinels within the liver, prompting them to release pro-inflammatory cytokines including tumour necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), and interleukin-1 beta (IL-1beta).

This inflammatory cascade does not remain confined to the liver. Elevated circulating cytokines enter the bloodstream and contribute to systemic inflammation, which has been linked to insulin resistance, cardiovascular disease, and impaired immune surveillance. The gut-liver axis also plays an important role: increased intestinal permeability (sometimes described informally as "leaky gut") allows bacterial products such as lipopolysaccharide (LPS) to reach the liver via the portal vein, further stimulating immune activation.

Over time, persistent immune activation within the liver leads to the recruitment of additional immune cells, including neutrophils and monocytes, which amplify tissue damage and drive fibrosis. Progression from simple steatosis to steatohepatitis and potentially cirrhosis involves immune, metabolic, and fibrogenic mechanisms acting together; immune activation is a major driver but not the sole one. Recognising that inflammation is both a cause and a consequence of fatty liver disease helps explain why the condition has such wide-ranging effects on overall health, including on the body's ability to mount effective immune responses to infection and other challenges.

Are people with fatty liver more vulnerable to infections?

Yes, fatty liver impairs Kupffer cell phagocytosis and natural killer cell function, and people with MASLD showed higher rates of severe outcomes during the COVID-19 pandemic.

People with fatty liver disease do appear to have an increased vulnerability to certain infections, largely because chronic hepatic inflammation impairs the normal function of immune cells responsible for pathogen clearance. Research suggests that Kupffer cells in fatty livers exhibit altered phagocytic activity, meaning they may be less efficient at engulfing and destroying bacteria and other pathogens that arrive from the gut.^[6][7] Natural killer cell function also appears to be reduced in the context of hepatic steatosis, potentially weakening one of the body's first lines of defence against viral infections. The evidence base for these mechanisms is still developing, and most data come from observational and experimental studies rather than large randomised trials.

Evidence gathered during the COVID-19 pandemic suggested that individuals with MASLD, particularly those with coexisting obesity, type 2 diabetes, or metabolic syndrome, were at greater risk of severe outcomes from SARS-CoV-2 infection.^[10][11] Interpreting this association is complicated by the fact that obesity and type 2 diabetes independently affect immune function, and disentangling the specific contribution of liver fat from these overlapping factors remains an active area of research.

Beyond viral infections, people with advanced fatty liver disease or cirrhosis face a well-recognised risk of bacterial infections, including spontaneous bacterial peritonitis and urinary tract infections, partly because the liver's capacity to synthesise complement proteins and acute-phase reactants is reduced. In earlier stages of fatty liver disease, some studies have suggested a possible increase in minor infections such as respiratory tract infections, but this association is less firmly established and should be interpreted cautiously.

People with chronic liver disease may be eligible for influenza and pneumococcal vaccinations on the NHS. It is worth discussing vaccination status with your GP, as up-to-date immunisation is one practical way to reduce infection risk. The NHS and UKHSA publish current eligibility criteria for these vaccines.

Which immune-related conditions are linked to fatty liver disease?

Fatty liver is associated with type 2 diabetes, cardiovascular disease, psoriasis, IBD, and emerging autoimmune conditions, largely through shared inflammatory and metabolic pathways.

Several conditions with inflammatory or immune components are associated with fatty liver disease, reflecting the broad impact of hepatic inflammation on systemic immune regulation. The associations below are based on observational and population-based data; in most cases, shared risk factors such as obesity and insulin resistance are likely to contribute alongside any direct immune mechanism, and causality has not been firmly established.

• Type 2 diabetes and insulin resistance: Chronic low-grade inflammation driven by fatty liver contributes to insulin resistance, which in turn impairs immune cell function, creating a bidirectional relationship between metabolic and immune dysregulation.

• Cardiovascular disease: Elevated inflammatory cytokines from the liver promote atherosclerosis, a process involving macrophage infiltration of arterial walls. Both conditions share metabolic risk factors, and the inflammatory component is one of several contributing pathways.

• Psoriasis and other inflammatory skin conditions: Population studies have found higher rates of MASLD among people with psoriasis, suggesting shared inflammatory pathways involving TNF-alpha and IL-17.^[7][8] The magnitude and direction of this association continue to be studied.

• Inflammatory bowel disease (IBD): The gut-liver axis links intestinal inflammation to hepatic immune activation, and fatty liver appears to be more prevalent among people with IBD than in the general population, though shared risk factors may partly explain this.

• Autoimmune conditions: There is emerging evidence that chronic systemic inflammation associated with fatty liver may lower the threshold for autoimmune activity, though this area of research is at an early stage and causality has not been established.

NICE guidance on the assessment and management of NAFLD (NG49, which uses NAFLD terminology corresponding to MASLD) recommends addressing metabolic risk factors holistically rather than treating each condition in isolation. A GP or specialist can help determine whether fatty liver is contributing to any immune-related symptoms a person is experiencing.

Can improving your liver health strengthen your immune response?

Yes, a 7 to 10 per cent reduction in body weight, a Mediterranean diet, and regular physical activity can reduce liver fat and lower circulating inflammatory markers.

Improving liver health through lifestyle changes can meaningfully strengthen immune function, with evidence showing that even modest reductions in liver fat lead to measurable decreases in systemic inflammation. NICE guidance (NG49) supports lifestyle intervention as the cornerstone of NAFLD/MASLD management, and the immune benefits of these changes are increasingly well documented.

Weight loss is the most effective intervention. NICE NG49 and international guidelines indicate that a sustained reduction in body weight of around 7 to 10 per cent is associated with significant reductions in hepatic inflammation and fibrosis, alongside falls in circulating inflammatory markers such as C-reactive protein (CRP) and IL-6.^[1][15] A Mediterranean-style dietary pattern, which is rich in vegetables, legumes, whole grains, oily fish, and olive oil, has been shown to reduce liver fat and improve metabolic parameters.^[16][17]

Physical activity independently reduces hepatic fat and improves immune cell function, even without significant weight loss. Both aerobic exercise and resistance training have demonstrated benefit in clinical studies. The UK Chief Medical Officers' physical activity guidelines recommend at least 150 minutes of moderate-intensity activity per week for adults, and this target is reflected in NHS guidance.^[12][13]

Alcohol reduction is important even in MASLD, as alcohol further burdens the liver and amplifies inflammatory signalling. The UK Chief Medical Officers' low-risk drinking guidelines advise consuming no more than 14 units of alcohol per week, spread across three or more days, with several alcohol-free days each week.^[14] People with fatty liver disease are generally advised to keep within or below this limit.

For people seeking structured support, online weight-management consultations are one route to accessing clinical guidance. Bolt Pharmacy is a GPhC-registered UK online pharmacy offering weight-management consultations with prescriber review and pharmacist support, where a range of clinically appropriate options may be considered. Addressing liver health as part of broader metabolic care is likely to yield the greatest immune benefit.

When should you see a GP about fatty liver and recurring illness?

See your GP if you have fatty liver and experience recurring infections, persistent fatigue, jaundice, abdominal swelling, or easy bruising, as these may indicate worsening liver function.

You should see your GP if you have a known or suspected diagnosis of fatty liver disease and are experiencing recurring infections, persistent fatigue, or symptoms that suggest your immune system may not be functioning normally. Fatty liver disease is often asymptomatic in its early stages, but certain warning signs warrant prompt medical review:

• Recurring or unusually severe infections, such as frequent chest infections, urinary tract infections, or skin infections that are slow to resolve

• Persistent fatigue or malaise that is disproportionate to your level of activity or sleep

• Jaundice (yellowing of the skin or whites of the eyes), dark urine, or pale stools, which may indicate worsening liver function

• Abdominal swelling or discomfort, particularly in the upper right abdomen

• Easy bruising or prolonged bleeding, which can indicate impaired liver synthesis of clotting factors

If you have not been formally assessed for fatty liver disease but have risk factors such as obesity, type 2 diabetes, high blood pressure, or high cholesterol, it is worth raising this with your GP. NICE guidance (NG49) recommends that people with these risk factors are assessed for NAFLD/MASLD, which may involve blood tests including liver function tests and fibrosis risk scoring. NICE NG49 specifically recommends the Enhanced Liver Fibrosis (ELF) test for assessing advanced fibrosis; local integrated care board (ICB) pathways may also use the FIB-4 or NAFLD Fibrosis Score (NFS) as initial triage tools. In some cases, imaging such as a liver ultrasound or elastography (for example, FibroScan) may be arranged. Your GP can advise on which pathway applies locally, and may refer to a hepatologist or gastroenterologist if advanced fibrosis or decompensation is suspected.

For urgent symptoms such as sudden severe abdominal pain, vomiting blood, or confusion, you should call 999 or go to your nearest accident and emergency department immediately. For non-emergency concerns that cannot wait for a routine GP appointment, NHS 111 can provide advice. Regular monitoring and early intervention remain the most effective ways to prevent fatty liver disease from progressing and to protect long-term immune health.

Scientific References

1. Metabolic dysfunction-associated steatotic liver disease (MASLD) [NG49].
2. Non-alcoholic fatty liver disease (NAFLD).
3. Spatial niche remodeling of senescent liver-resident immune cells and its role in chronic liver diseases.
4. Metabolic Dysfunction-Associated Steatotic Liver Disease, Recent Revision of Terminology and Its Implications.
5. Current Update on Nomenclature, Diagnosis, and Management of Metabolic Dysfunction-associated Steatotic Liver Disease: Radiologists' Perspective.
6. Phagocytic function of Kupffer cells in mouse nonalcoholic fatty liver disease.
7. Hepatic immune microenvironment dynamics in severe obesity and post-bariatric surgery: insights from immunohistochemical analysis.
8. Single-cell atlas of human liver and blood immune cells across fatty liver disease stages reveals distinct signatures linked to liver dysfunction and fibrogenesis.
9. CD44 in Group 1 Innate Lymphoid Cells Impacts the Development and Progression of Steatohepatitis.
10. NAFLD and NASH are obesity-independent risk factors in COVID-19.
11. The global prevalence and impact of steatotic liver disease and viral infections: A systematic review and meta-analysis.
12. Physical activity guidelines: UK Chief Medical Officers' report.
13. Physical activity guidelines for adults aged 19 to 64.
14. Alcohol consumption: advice on low risk drinking.
15. Impact of weight loss and reduction of ultra-processed foods on liver fat content in MASLD: A randomized controlled trial.
16. A culturally adapted online Mediterranean diet intervention for metabolic dysfunction-associated steatotic liver disease (TIMA): study protocol for a randomized controlled trial.
17. Very low energy ketogenic diet vs. Mediterranean diet for MASLD: Superior steatosis reduction in a randomised pilot study.
18. Structured Exercise Interventions and Hepatic-Metabolic Outcomes in Adults with MASLD: A Narrative Review of Randomized Controlled Trials.
19. The Effects of a Short-Term Combined Exercise Program on Liver Steatosis Indices and the Lipidemic and Glycemic Profile in NAFLD Individuals: A Pilot Study.
20. Using the ELF test, FIB-4 and NAFLD fibrosis score to assess advanced fibrosis.

Frequently Asked Questions