How long do I need to fast to decrease inflammation?

November 22, 2025 •

4 min read

Recent studies have revealed a complex relationship between fasting duration and inflammation markers, showing that prolonged periods without food can sometimes initially increase inflammation before it falls. To understand how long you need to fast to decrease inflammation, it's crucial to distinguish between different fasting protocols and their distinct biological effects on the body.

Quick Summary

The ideal fasting duration to reduce inflammation varies significantly by protocol. Shorter, intermittent fasts can effectively lower inflammatory markers. Longer, prolonged fasts may trigger a temporary inflammatory response before decreasing inflammation after refeeding.

Key Points

Intermittent vs. Prolonged Fasting: Shorter fasts (under 48 hours) typically reduce inflammation, while longer fasts (over 48 hours) may cause a temporary increase.
Start with Shorter Windows: Time-restricted eating, such as the 16/8 method, is a well-regarded approach to consistently decrease inflammation over time.
The Role of Autophagy: Fasting triggers autophagy, a cellular repair process that can reduce oxidative stress and aid in calming inflammation.
Inflammatory Spike during Prolonged Fasting: Be aware that prolonged fasts may cause a spike in inflammatory markers like CRP, especially in overweight individuals.
Refeeding is Important: The inflammatory increase from a prolonged fast can often normalize or decrease below baseline after a proper refeeding period.
Consult a Doctor: Always seek medical advice before beginning any fasting protocol, especially if considering prolonged fasting, due to potential risks.

Intermittent Fasting (IF) and Its Anti-Inflammatory Effects

For many, the sweet spot for reducing inflammation lies in intermittent fasting (IF), rather than more prolonged fasts. Research indicates that shorter, regular fasting periods can help calm the body's inflammatory response. A key discovery from a Mount Sinai study found that intermittent fasting led to a significant drop in inflammatory monocytes, a type of white blood cell that contributes to inflammation. The researchers suggest that our modern, frequent eating habits may keep these cells at unnecessarily high levels. By extending the time between meals, IF may help normalize these immune cell counts.

Key mechanisms behind IF's anti-inflammatory effects include:

Reduction of Inflammasome Activity: Fasting has been shown to increase levels of arachidonic acid, a chemical that can inhibit the NLRP3 inflammasome, a protein structure that triggers inflammation. This provides a direct biochemical pathway for reducing inflammatory signals.
Improved Metabolic Health: Conditions like insulin resistance are strongly linked to chronic, low-grade inflammation. Several studies have found that intermittent fasting and alternate-day fasting are effective at reducing insulin resistance, thereby addressing one of inflammation's root causes.
Enhanced Autophagy: Fasting triggers autophagy, a cellular process that cleans out damaged cells and proteins. This cellular cleanup reduces oxidative stress and can directly contribute to lower inflammation.

Popular Intermittent Fasting Protocols for Reducing Inflammation

Time-Restricted Eating (16/8): Eating all daily food within an 8-hour window and fasting for 16 hours. A November 2024 YouTube presentation referenced recent studies showing time-restricted eating reduces inflammation and improves heart health.
24-Hour Fasts: Fasting for a full 24 hours, often done once or twice a week. Some studies suggest that fasting over 24 hours can decrease inflammation by reducing oxidative stress.

The Paradox of Prolonged Fasting (PF)

Contrary to the effects of intermittent fasting, prolonged fasting (defined as 48 hours or more) may elicit a different, more complex response from the body. Recent reviews and studies challenge the popular belief that all fasting decreases inflammation.

The Pro-Inflammatory Spike

Elevated Markers: A 2025 study in Molecular Metabolism found that medically supervised prolonged water-only fasting (around 10 days) actually led to a significant increase in circulating high-sensitivity C-reactive protein (hsCRP). Other inflammatory markers, like IL-8 and ferritin, also rose.
Transient Effect: Researchers theorize this might be an adaptive, temporary immune response. For example, studies have shown that hsCRP levels, while increasing during a fast, can drop below baseline levels after a period of refeeding.

Potential Risks of Prolonged Fasting

Cardiovascular and Thrombotic Risk: The increase in inflammatory markers and heightened platelet activity during prolonged fasting may exacerbate cardiovascular risk, especially for individuals with pre-existing conditions like atherosclerosis.
Nutrient Deficiencies: Fasting for extended periods can lead to malnutrition and loss of muscle mass without proper monitoring.

Comparison Table: IF vs. Prolonged Fasting for Inflammation


Feature	Intermittent Fasting (16–24 hours)	Prolonged Fasting (48+ hours)
Typical Duration	12–24 hour windows, repeated regularly (e.g., 16/8, 5:2)	Continuous fasting for two or more days
Initial Inflammatory Response	Generally anti-inflammatory; reduces monocytes and inflammasome activity.	Often triggers a temporary increase in inflammatory markers like CRP and IL-6.
Long-Term Inflammation Effects	Reduces chronic low-grade inflammation, improving overall metabolic markers.	More complex and variable. Long-term studies are limited; some suggest effects are transient and markers normalize after refeeding.
Risk Profile	Generally low for healthy individuals; minimal risk of nutrient deficiency.	Higher risk profile, especially for those with pre-existing conditions. Requires medical supervision.
Primary Mechanism	Modulates immune cell function, reduces oxidative stress, improves metabolism.	Complex proteomic changes, metabolic adaptations, potential acute immune activation.

Medical Guidance and Considerations

The most important takeaway is that no single duration fits all. For most people seeking to decrease inflammation, a consistent intermittent fasting schedule is the most studied and safest starting point. Prolonged fasting should always be undertaken with medical supervision, especially for those with pre-existing conditions or on medications. It is critical to understand the nuanced effects on the body and not assume that longer is always better. As demonstrated by the recent research showing an inflammatory spike with longer fasts, the body's response is highly context-dependent.

Conclusion: Personalized Approach is Key

Ultimately, how long you need to fast to decrease inflammation is not a simple question with a single answer. For those seeking a safe and effective dietary intervention, intermittent fasting methods like time-restricted eating (16/8) have demonstrated consistent anti-inflammatory benefits and improved metabolic health over the short to medium term. In contrast, prolonged fasts of 48 hours or more may temporarily increase inflammation, although markers can decrease again post-refeeding. The long-term effects of repeated prolonged fasting are still under investigation, and the risks for certain individuals warrant medical oversight. An individualized approach that aligns with personal health status, guided by a healthcare professional, is essential for a safe and effective fasting regimen to combat inflammation.

For more in-depth scientific research on this topic, consult the study: Prolonged fasting promotes systemic inflammation and platelet activation in humans.

Frequently Asked Questions

Yes, fasting for 24 hours can help decrease inflammation. Studies have shown that fasts of this length can reduce oxidative stress in cells and lower the number of circulating inflammatory monocytes.

For managing chronic inflammation, intermittent fasting protocols like time-restricted eating (e.g., 16/8) are a good place to start. They have shown consistent benefits in reducing inflammatory markers and improving metabolic health.

Recent studies suggest that prolonged fasts of 48 hours or more may cause a temporary increase in certain inflammatory markers, such as CRP, during the fasting period. The effect is complex and might be a transient, adaptive response.

No, the inflammatory increase from prolonged fasting is often temporary. Some studies show that after a refeeding period, inflammatory markers can return to baseline or even drop below pre-fasting levels.

Fasting can reduce inflammatory cells, specifically monocytes, through mechanisms involving metabolic changes and cellular processes like autophagy. It may also inhibit the activity of the NLRP3 inflammasome, which helps trigger inflammation.

Prolonged fasting should be avoided by pregnant or breastfeeding individuals, those with a history of eating disorders, and people with certain medical conditions, including cardiovascular or thrombotic disorders, without strict medical supervision.

Yes, combining intermittent fasting with an anti-inflammatory diet, rich in healthy fats, lean protein, fruits, and vegetables, can further enhance benefits and support overall health.