Inflammation in the body is triggered by your immune system responding to threats, but the list of things that can set it off is surprisingly long. Some causes are obvious, like infections or injuries. Others are less intuitive: the food you eat, the stress you carry, the air you breathe, and even excess body fat can all keep your immune system in a sustained state of alert. Understanding these triggers matters because chronic, low-grade inflammation is linked to heart disease, type 2 diabetes, and autoimmune conditions.
How Inflammation Actually Works
When your body detects damage or an invader, immune cells like neutrophils and macrophages rush to the site. These cells release signaling molecules, including cytokines like TNF-alpha and IL-6, that recruit more immune cells and increase blood flow to the area. That’s what causes the redness, swelling, warmth, and pain you associate with inflammation. In an acute scenario (a cut, a sprained ankle, a cold), this process resolves within days as the threat is cleared.
Chronic inflammation is different. Instead of a loud, short-lived alarm, it’s a quiet hum that never shuts off. The same signaling pathways stay activated at a low level, and the immune molecules meant to fight a temporary threat start damaging healthy tissue over time. This is the type of inflammation tied to serious disease, and it can persist for months or years without obvious symptoms.
Diet: Sugar, Trans Fats, and Processed Foods
What you eat has a direct effect on your inflammatory state. Trans fats are one of the clearest dietary triggers. Research published in Frontiers in Immunology found that trans fatty acids (specifically elaidic acid, the most common form in processed foods) cause a cascade of problems starting in your gut. They increase populations of bacteria that produce hydrogen sulfide, a compound that breaks down the protective mucus lining of your intestines. With that barrier weakened, inflammatory signals increase.
Trans fats also stimulate macrophages to release IL-12, a cytokine that shifts immune cells in your gut lining toward a more inflammatory profile. The downstream effects aren’t limited to your digestive system. Animal studies showed that liver inflammation markers, including TNF-alpha, IL-6, and IL-1 beta, rose significantly with trans fat intake compared to a normal diet, and rose even higher than with other types of high-fat diets.
Refined sugar and highly processed carbohydrates trigger similar pathways by promoting spikes in blood sugar and insulin, both of which activate inflammatory signaling. Diets heavy in processed meats, fried foods, and sugary drinks consistently correlate with higher levels of circulating inflammatory markers.
Chronic Psychological Stress
Stress doesn’t just feel bad. It changes how your immune system functions at a cellular level. Your body normally uses cortisol, a hormone released during stress, to dial down inflammation. It’s part of a built-in feedback loop: the immune system ramps up, cortisol tells it to stand down. But under prolonged stress, something breaks.
A landmark study from the Proceedings of the National Academy of Sciences found that chronic stress leads to glucocorticoid receptor resistance, meaning your immune cells lose their sensitivity to cortisol’s “stand down” signal. Without that brake, the inflammatory response runs longer and hits harder than it should. The researchers showed that as immune cells became more resistant to cortisol, they produced more TNF-alpha and IL-6, two of the body’s primary inflammatory molecules. This helps explain why people under chronic stress are more vulnerable to autoimmune flares, cardiovascular disease, and even worse cold symptoms. Their immune systems aren’t failing; they’re failing to turn off.
Excess Body Fat, Especially Visceral Fat
Fat tissue isn’t just a passive energy reserve. It actively secretes inflammatory molecules. Visceral fat, the type that accumulates around your organs and in your abdomen, is especially active. Research in The Lancet’s eBioMedicine confirmed that visceral fat tissue releases elevated levels of TNF-alpha, IL-1 beta, and IL-6, the same cytokines your body produces during infection. Population studies have consistently linked this chronic, low-level inflammation from fat tissue to insulin resistance and metabolic syndrome.
TNF-alpha from visceral fat directly interferes with insulin signaling, making cells less responsive to insulin and pushing blood sugar higher. This creates a vicious cycle: inflammation promotes insulin resistance, insulin resistance promotes more fat storage, and more fat storage produces more inflammation. It’s one of the core mechanisms connecting obesity to type 2 diabetes and heart disease.
Infections That Never Fully Leave
Acute infections like the flu cause temporary inflammation that resolves once the virus is cleared. But several common viruses never fully leave your body. Instead, they enter a dormant state and can reactivate periodically, keeping your immune system partially engaged for years or decades.
The most well-studied examples are herpesviruses: Epstein-Barr virus (the cause of mono, carried by roughly 90% of adults), cytomegalovirus (CMV), and varicella-zoster (the chickenpox virus that can reactivate as shingles). Other persistent viruses include HHV-6, HHV-7, and certain polyomaviruses like JC virus and BK virus. These viruses have evolved strategies to evade immune detection, but their presence still sustains a baseline level of immune activation. As your immune system ages or becomes stressed, these latent viruses are more likely to reactivate, driving further inflammation. This mechanism is also under investigation in long COVID, where viral persistence may explain ongoing inflammatory symptoms months after the initial infection.
Autoimmune Conditions
In autoimmune diseases, your immune system mistakes your own tissues for threats and attacks them. This produces sustained, often severe inflammation in specific organs or throughout the body. Johns Hopkins classifies autoimmune diseases into two categories: organ-specific (targeting one tissue) and systemic (affecting multiple organs).
The major systemic autoimmune diseases include:
- Rheumatoid arthritis: targets the synovium, the membrane lining peripheral joints like hands, elbows, shoulders, knees, and hips
- Systemic lupus erythematosus: affects joints, kidneys, heart, muscles, nervous system, skin, lungs, and the gastrointestinal system
- Scleroderma: causes hardening and thickening of skin and connective tissue, often involving internal organs
- Dermatomyositis: targets the skin and striated muscles, and frequently affects joints and lungs
In these conditions, the body produces antibodies against its own proteins, particularly against components found in nearly every cell type, like DNA-protein complexes. Because these targets exist throughout the body, the resulting inflammation can damage multiple organ systems simultaneously.
Air Pollution and Environmental Toxins
Fine particulate matter (PM2.5), the tiny particles in vehicle exhaust, wildfire smoke, and industrial emissions, triggers inflammation even in healthy people. These particles are small enough to pass from your lungs into your bloodstream, where they set off an inflammatory chain reaction involving fat-derived signaling molecules.
Research published in Science of the Total Environment mapped the pathway: PM2.5 exposure activates a lipid called ceramide-1-phosphate, which triggers the release of arachidonic acid from cell membranes. Arachidonic acid is then converted into prostaglandins and leukotrienes, potent inflammatory compounds. In the study, PM2.5 exposure was associated with a 12.9% increase in arachidonic acid levels over just three days, and that increase mediated a 27.1% rise in the inflammatory marker IL-8 over a week. These are the same prostaglandin and leukotriene pathways activated in asthma and allergic reactions, which is why air pollution worsens respiratory and cardiovascular conditions.
Other Common Triggers
Several additional factors contribute to chronic inflammation. Poor sleep consistently raises inflammatory markers; even a few nights of restricted sleep (under six hours) increases circulating IL-6 and CRP. Smoking introduces thousands of toxic compounds that directly damage tissue and activate immune responses in the lungs and blood vessels. Excessive alcohol consumption damages the gut lining, allowing bacterial products to leak into the bloodstream and trigger widespread immune activation. Sedentary behavior is independently associated with higher inflammatory markers, even after accounting for body weight.
How Inflammation Is Measured
If you’re concerned about chronic inflammation, the most common screening tool is a high-sensitivity C-reactive protein (hs-CRP) test, a simple blood draw. CRP is a protein your liver produces in response to inflammation, and the high-sensitivity version of the test can detect the low levels associated with chronic inflammation rather than just acute infections. According to the Mayo Clinic, an hs-CRP below 2.0 mg/L indicates lower cardiovascular risk, while 2.0 mg/L or above signals higher risk of heart attack. Values well above that range suggest significant systemic inflammation that warrants further investigation. Your doctor may also check other markers like IL-6 or erythrocyte sedimentation rate depending on the suspected cause.
Because so many factors feed into inflammation, the most effective approach for most people involves multiple fronts: reducing processed food and trans fat intake, managing stress, staying physically active, maintaining a healthy weight, and minimizing exposure to air pollution and tobacco smoke. Each of these individually moves inflammatory markers in the right direction, and together they can meaningfully shift your baseline inflammatory state.