The main cause of inflammation in the body depends on whether it’s short-lived or ongoing. Acute inflammation is triggered by injury or infection and resolves within days. Chronic inflammation, the kind most people are concerned about, is driven primarily by the immune system responding to persistent internal stressors like excess body fat, prolonged psychological stress, smoking, and high cholesterol. Of these, excess visceral fat is one of the most common and well-documented drivers of the low-grade, system-wide inflammation linked to heart disease, type 2 diabetes, and other chronic conditions.
How Acute Inflammation Works
When you cut your finger or catch a cold, your immune system launches a rapid response. Blood flow increases to the affected area, white blood cells rush in, and you feel the familiar signs: redness, warmth, swelling, and pain. This is acute inflammation, and it’s entirely beneficial. It fights off invading bacteria or viruses, clears damaged tissue, and kicks off healing. Once the threat is handled, the process shuts down and everything returns to normal, usually within a few days to a couple of weeks.
When Inflammation Becomes Chronic
Problems start when the immune system never gets the signal to stand down. Instead of a short burst of activity, it keeps pumping out white blood cells and chemical signals that sustain the inflammatory response indefinitely. From the body’s perspective, it’s under constant attack, so it keeps fighting even when there’s no infection or injury to resolve.
This chronic, low-grade inflammation often produces no obvious symptoms for years. You won’t necessarily feel swelling or pain. Instead, the damage accumulates quietly in blood vessels, organs, and tissues, raising the risk of heart disease, type 2 diabetes, certain cancers, and neurodegenerative conditions. Unlike a swollen ankle, chronic inflammation is measured through blood tests rather than visible signs.
Visceral Fat: A Primary Driver
Excess body fat, particularly the deep visceral fat that surrounds your organs, is one of the most significant causes of chronic inflammation. The immune system can treat these fat cells as a threat, attacking them with white blood cells and sustaining an ongoing inflammatory response. Visceral fat tissue actively secretes inflammatory signaling molecules, including TNF-alpha, IL-1 beta, and IL-6, all of which circulate through the bloodstream and affect the entire body.
Population studies have consistently linked this fat-driven inflammation to insulin resistance, the precursor to type 2 diabetes. TNF-alpha, one of the key molecules released by visceral fat, directly promotes insulin resistance in surrounding tissues. IL-1 beta and IL-6 trigger the liver to produce C-reactive protein (CRP), a marker doctors use to measure systemic inflammation. Notably, visceral fat produces significantly more of these inflammatory molecules than the subcutaneous fat just beneath your skin, which helps explain why waist circumference matters more than overall weight for predicting inflammatory disease risk.
Chronic Stress and Immune Dysregulation
Your body has a built-in mechanism for turning off inflammation: the stress hormone cortisol. Under normal circumstances, cortisol binds to receptors on immune cells and tells them to dial back the inflammatory response. But when you’re under chronic psychological stress, something counterintuitive happens. The problem isn’t that cortisol levels are too low or too high. It’s that immune cells stop listening to cortisol’s signal.
This phenomenon, called glucocorticoid receptor resistance, means the off-switch for inflammation stops working. Research published in the Proceedings of the National Academy of Sciences found that chronic stress changes the ratio of receptor types on immune cells, favoring a version that actively blocks cortisol’s anti-inflammatory message. Without that regulation, inflammatory responses become more intense and last longer. This helps explain why people under sustained stress are more vulnerable to asthma flare-ups, autoimmune episodes, cardiovascular disease, and even worse cold symptoms. The infection itself isn’t more severe; the body simply can’t control its own inflammatory reaction to it.
Cholesterol, Smoking, and Air Pollution
High levels of LDL cholesterol trigger an inflammatory response inside artery walls. White blood cells move in to deal with cholesterol deposits, creating plaques that narrow blood vessels over time. This is why inflammation and heart disease are so tightly linked: the arterial damage is itself an inflammatory process, not just a plumbing problem.
Smoking introduces toxins that have a direct, well-established connection to systemic inflammation. The chemicals in cigarette smoke damage tissue throughout the airways and bloodstream, prompting a sustained immune response that persists as long as the exposure continues.
Air pollution works through a similar mechanism. Fine particulate matter smaller than 2.5 micrometers (PM2.5), mostly produced by combustion, penetrates deep into the lungs. These particles generate reactive oxygen species, highly unstable molecules that damage cells and trigger inflammatory cascades in both the respiratory and cardiovascular systems. This is why living near heavy traffic or in areas with poor air quality is associated with higher rates of heart and lung disease even in people who don’t smoke.
Aging and Cellular Buildup
As you age, your body accumulates senescent cells. These are cells that have stopped dividing but haven’t been cleared away by the immune system. Instead of sitting quietly, they release a cocktail of inflammatory molecules into surrounding tissue. This process contributes to what researchers call “inflammaging,” a steady rise in baseline inflammation that accelerates tissue breakdown and increases disease risk with every passing decade.
Animal research has shown that selectively removing these senescent cells delays age-related disorders, which strongly suggests they’re a meaningful source of the inflammatory markers found in aging blood. The accumulation is gradual, which is partly why inflammatory diseases cluster in the second half of life. Your immune system is simultaneously becoming less precise and dealing with a growing number of these inflammatory cell factories throughout your tissues and organs.
How Chronic Inflammation Is Measured
The most common blood test for systemic inflammation is high-sensitivity C-reactive protein (hs-CRP). Your liver produces CRP in response to inflammatory signals, so its level in blood reflects how much inflammation is happening body-wide. The risk categories for cardiovascular events break down simply: below 1.0 mg/L is low risk, 1.0 to 3.0 mg/L is intermediate, and above 3.0 mg/L is high risk. A reading above 10.0 mg/L typically indicates an active acute inflammation, like an infection, rather than the chronic kind.
A single elevated reading doesn’t tell you much on its own, since even a minor illness can spike CRP temporarily. Patterns over time are more informative. If your hs-CRP is persistently in the intermediate or high range without an obvious infection, that points to chronic inflammation driven by one or more of the factors above: excess visceral fat, ongoing stress, smoking, high cholesterol, or environmental exposures. Addressing those root causes is what brings the numbers down.