Can Fasting Affect Inflammation? Exploring the Complex Relationship

October 16, 2025 •

4 min read

According to a 2024 study, prolonged fasting can cause a temporary, acute increase in inflammatory markers like C-reactive protein (CRP), challenging the common belief of constant anti-inflammatory effects. This raises the question: Can fasting affect inflammation? The answer is complex and depends heavily on the fasting duration and individual metabolic context.

Quick Summary

The impact of fasting on inflammation varies significantly by duration. Short-term, intermittent fasting may offer anti-inflammatory benefits, but prolonged fasts often trigger a temporary pro-inflammatory response that reverses upon refeeding.

Key Points

Duration Matters: The effect of fasting on inflammation varies significantly depending on the length of the fast; intermittent fasting typically lowers inflammation while prolonged fasting can cause a temporary spike.
Intermittent Fasting (IF) Benefits: Shorter fasting periods, like 16:8 or time-restricted eating, have been shown to reduce inflammatory markers such as CRP and suppress pro-inflammatory cells.
Prolonged Fasting Paradox: Fasting for more than 48 hours can trigger an acute, temporary increase in inflammatory markers like CRP and IL-6, which may represent a transient, adaptive metabolic stress response.
The Refeeding Effect: After a prolonged fast, inflammatory markers often drop below baseline levels during the refeeding period, suggesting a potential long-term benefit.
Multiple Mechanisms: Fasting can reduce inflammation through various mechanisms, including inhibiting the NLRP3 inflammasome, increasing anti-inflammatory lipids, and inducing cellular repair processes like autophagy.
Consider Individual Health: The fasting-inflammation relationship is highly context-dependent, influenced by an individual's baseline metabolic health, diet, and genetics.

The Nuanced Relationship Between Fasting and Inflammation

Fasting is a practice with deep historical roots, from religious rituals to modern health trends. While often celebrated for its potential to combat inflammation, scientific evidence shows a more complex picture. For shorter periods, such as time-restricted eating, the body's response is often anti-inflammatory. However, prolonged fasting lasting more than 48 hours can trigger a temporary increase in certain inflammatory markers. Understanding these different physiological responses is crucial for anyone considering fasting as a health strategy.

The Anti-Inflammatory Effects of Intermittent Fasting

Intermittent fasting (IF), particularly regimens like time-restricted eating (e.g., 16:8), shows promising anti-inflammatory effects by giving the body a break from constant digestion. This periodic stress response can activate cellular repair processes and modulate immune function.

Reduction of pro-inflammatory cells: Studies have demonstrated that intermittent fasting can reduce the release of monocytes, a type of white blood cell that promotes inflammation. The monocytes that remain are found to be less inflammatory.
Suppression of inflammasome activity: Research suggests that fasting can suppress the activity of the NLRP3 inflammasome, a protein complex that helps trigger inflammatory responses. This mechanism could be a key factor in how fasting protects against inflammation-related chronic diseases.
Rise in anti-inflammatory lipids: A study found that a 24-hour fast increased blood levels of arachidonic acid, a lipid known to inhibit inflammation. This offers a potential molecular pathway for fasting's anti-inflammatory effects.
Improved oxidative stress markers: Some intermittent fasting protocols have been shown to reduce markers of oxidative stress and upregulate antioxidant enzymes, which helps mitigate inflammation.

The Paradox of Prolonged Fasting and Acute Inflammation

In contrast to shorter fasts, prolonged fasting—defined as abstaining from energy intake for 48 hours or more—can provoke a paradoxical acute pro-inflammatory response. A 2025 scoping review of studies on prolonged fasting found that many participants experienced an increase in inflammatory markers, including C-reactive protein (CRP), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-α).

Temporary stress response: The inflammatory spike is likely a transient, adaptive stress response as the body undergoes major metabolic shifts. As the body switches from using glucose to ketone bodies for fuel, it can temporarily elevate inflammatory signals.
Refeeding effect: Studies show that after a period of prolonged fasting, inflammatory markers often decrease significantly during the refeeding period, sometimes dropping below baseline levels. This suggests the inflammatory phase is a temporary hurdle before the anti-inflammatory benefits take effect.
Increased risk in vulnerable individuals: The temporary inflammatory and pro-thrombotic state induced by prolonged fasting may be risky for individuals with pre-existing conditions like cardiovascular disease or advanced atherosclerosis.

Comparing Fasting Protocols and Their Impact on Inflammation

To illustrate the differences, consider the impact of different fasting methods on inflammatory markers, particularly C-reactive protein (CRP).


Feature	Intermittent Fasting (e.g., 16:8)	Prolonged Fasting (e.g., 48+ hours)
Typical Duration	12-24 hours	48 hours to several weeks
Initial Inflammatory Effect	Generally anti-inflammatory	Transiently pro-inflammatory
Effect on CRP	Significant reduction, especially in overweight/obese individuals	Acute increase during the fast
Post-Fasting Effect	Sustained anti-inflammatory benefits	Markers often decrease below baseline during refeeding
Underlying Mechanism	Reduction of inflammatory monocytes, suppression of NLRP3 inflammasome	Adaptive metabolic stress response, macrophage activation
Risk for Vulnerable People	Lower risk, considered safer	Potentially risky for those with chronic inflammatory or cardiovascular conditions

Factors Influencing Fasting's Effect

The body's response to fasting is not a one-size-fits-all phenomenon. Several factors can influence how fasting affects inflammation:

Metabolic health: A person's metabolic state, including baseline weight and insulin sensitivity, plays a crucial role. Those with excess adipose tissue often have higher baseline inflammation, and their response to fasting may differ.
Dietary composition: The quality of food consumed during eating windows can significantly impact inflammation. A healthy, nutrient-dense diet can enhance the anti-inflammatory benefits of fasting. For example, studies suggest the anti-inflammatory benefits of Ramadan fasting may be linked to specific dietary restrictions.
Genetics and epigenetics: Individual genetic makeup and other biological variables can dictate the body's inflammatory response to fasting, explaining some of the variability seen in studies.

Conclusion: A Context-Dependent Approach

Can fasting affect inflammation? The scientific consensus is a resounding "yes," but the nature of that effect depends entirely on the context. Intermittent fasting methods generally show anti-inflammatory benefits, likely by promoting cellular repair and modulating immune responses. Conversely, prolonged fasting can cause a temporary inflammatory spike, which seems to be a part of a larger metabolic adaptation, with potential long-term anti-inflammatory effects realized after refeeding.

For most individuals, particularly those with conditions linked to chronic inflammation like obesity, starting with shorter, time-restricted eating patterns may be the safer approach to potentially reap benefits without the acute stress response of prolonged fasts. Given the individual variability and potential risks, especially with longer fasts, it is vital to consult with a healthcare professional before making significant dietary changes. The right fasting strategy is a personalized one, tailored to your unique health profile and goals.

Learn more about the differences between calorie restriction and fasting, and their effects on health here.

Frequently Asked Questions

No, not all fasting is the same. While shorter, intermittent fasting periods often have an anti-inflammatory effect, prolonged fasts (more than 48 hours) can cause a temporary, acute increase in inflammatory markers before they potentially fall to or below baseline levels after refeeding.

Intermittent fasting (IF) is generally associated with a decrease in inflammatory markers, particularly over a period of weeks to months. In contrast, prolonged fasting is linked to an initial, acute increase in inflammation during the fasting period itself, which then tends to reverse during refeeding.

This effect is believed to be a physiological stress response that occurs as the body shifts metabolic pathways due to a lack of nutrients. It can involve the activation of certain immune cells and the release of inflammatory cytokines, which is a key adaptation to nutrient deprivation.

Commonly studied inflammatory markers include C-reactive protein (CRP), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-α). Studies show variable results depending on the fasting type, with some showing changes in CRP and others showing no consistent effect on IL-6 and TNF-α.

Yes, for individuals with pre-existing conditions such as advanced atherosclerosis or certain coagulation disorders, the temporary spike in inflammation and related increase in platelet activity during prolonged fasting could pose a cardiovascular risk.

Yes, a healthy and nutrient-dense diet during eating windows can enhance the anti-inflammatory benefits of fasting. The overall quality of your diet, including avoiding pro-inflammatory foods, works synergistically with fasting to reduce systemic inflammation.

Prolonged fasting should be approached with caution and, ideally, under medical supervision, especially for individuals with underlying health conditions. Due to the temporary inflammatory and potential pro-thrombotic risks, it's safer for most people to start with gentler intermittent fasting methods.