How Long to Fast to Reduce Inflammation? Understanding the Optimal Duration

October 25, 2025 •

4 min read

Chronic inflammation is a root cause of many health issues, and some experts suggest many of us eat too frequently, which perpetuates inflammatory pathways. Fasting has emerged as a potential strategy, but knowing how long to fast to reduce inflammation is crucial for effectiveness and safety.

Quick Summary

This article explores various fasting durations, from intermittent to prolonged, detailing the evidence behind each approach and their potential effects on inflammatory markers like CRP.

Key Points

Optimal Duration Varies: Shorter fasts (16-24 hours) consistently reduce inflammation, while prolonged fasts (48+ hours) show a more complex, and potentially risky, inflammatory response.
16:8 is a Good Starting Point: The 16:8 intermittent fasting method is a popular and relatively safe option for beginners looking to achieve anti-inflammatory benefits.
Prolonged Fasting Requires Caution: Fasting for more than 48 hours can temporarily increase inflammatory markers and should only be done under medical supervision.
Diet During Eating Windows Matters: To maximize the anti-inflammatory effects of fasting, you should focus on consuming nutrient-dense, anti-inflammatory foods during eating periods.
Arachidonic Acid Plays a Role: Fasting increases levels of arachidonic acid, which helps suppress the NLRP3 inflammasome, a key driver of inflammation.
Refeeding is Critical for Prolonged Fasts: For longer fasts, the real anti-inflammatory benefits may appear during the post-fasting refeeding period, not during the fast itself.

The Science Behind Fasting and Inflammation

Fasting is an ancient practice gaining modern scientific attention for its health benefits. The mechanism by which fasting can influence inflammation is complex and relates to the body's metabolic switch from burning glucose to burning fat for energy. This process, known as metabolic switching, can initiate a cascade of cellular events that include cellular repair (autophagy) and immune system modulation.

Recent research has identified a potential new mechanism, involving a chemical called arachidonic acid, which increases during fasting and helps suppress the NLRP3 inflammasome, a protein complex that triggers inflammation. By inhibiting this inflammasome, fasting may offer protection against chronic inflammatory diseases associated with a high-calorie Western diet.

Short-Term Intermittent Fasting (12–24 Hours)

This category includes the most popular and generally well-tolerated fasting methods. For many, this is the safest and most sustainable approach to garnering anti-inflammatory benefits.

The 16:8 Method: This involves fasting for 16 hours and restricting eating to an 8-hour window. As a starting point, this method is popular because it often involves simply skipping breakfast and finishing dinner a little earlier. Studies suggest that refraining from food for 16-24 hours allows the body to perform repair and recovery mechanisms, helping to reduce inflammation.
The 5:2 Method: This involves eating normally for five days of the week and restricting calories to around 500-600 on two non-consecutive days. This approach provides periodic calorie restriction, which has also been linked to reduced inflammation.
Eat-Stop-Eat (24-hour fast): This involves fasting for a full 24 hours once or twice per week, typically from dinner to dinner or lunch to lunch. One study found that fasting for more than 24 hours lowered inflammation by reducing oxidative stress in the cells.

The Nuances of Prolonged Fasting (48+ Hours)

While shorter fasts show consistent anti-inflammatory benefits, the evidence for prolonged fasting (PF) is more complex and potentially contradictory. Recent systematic reviews and studies suggest that prolonged fasting (typically defined as ≥48 hours) can lead to a temporary increase in inflammatory markers, such as C-reactive protein (CRP).

Researchers theorize that this is an acute, adaptive response rather than a pathological one, possibly signaling tissue repair processes. Interestingly, these elevated inflammatory markers often return to or fall below baseline levels after the refeeding period. This suggests that the timing of measurement is critical and that the full benefit may manifest after the fast, not necessarily during it. However, the transient inflammatory spike during prolonged fasting could be a concern for individuals with pre-existing inflammatory or cardiovascular conditions.

Comparison of Fasting Methods and Their Effect on Inflammation

To illustrate the different effects, consider the following comparison of common fasting protocols.


Fasting Method	Duration	Typical Effect on Inflammation	Key Considerations
Time-Restricted Eating (e.g., 16:8)	16 hours daily	Generally reduces inflammation over time.	Beginner-friendly, sustainable, less risk of side effects.
24-Hour Fast (Eat-Stop-Eat)	24 hours, 1-2 times/week	Reduces oxidative stress and inflammation.	Can cause temporary fatigue or headaches.
5:2 Method	5 regular days, 2 low-calorie days	Decreases overall inflammation markers.	Focus on nutrient-dense foods on low-calorie days.
Prolonged Fasting (48+ hours)	≥48 hours, or longer	Initial temporary increase in inflammation, followed by a decrease upon refeeding.	Higher risk profile, requires medical supervision due to potential adverse effects.

The Importance of What You Eat When You Don't Fast

Fasting is one piece of the puzzle; the other is nutrition during your eating window. Adopting an anti-inflammatory diet is crucial for supporting fasting's effects and is linked to better outcomes. Focus on foods like:

Oily fish: High in anti-inflammatory omega-3 fatty acids.
Fruits and Vegetables: Rich in antioxidants and phytochemicals.
Whole Grains: Provide fiber and nutrients without the inflammatory spike of refined carbs.
Nuts and Seeds: Good source of healthy fats.
Olive Oil: A staple of the Mediterranean diet, known for its anti-inflammatory properties.

Practical Tips for Starting a Fasting Protocol

If you're new to fasting, it's wise to start slow and listen to your body. Starting with a 12-hour overnight fast is a simple and effective first step. Ensure you stay hydrated by drinking plenty of water, and consider incorporating unsweetened black coffee or herbal tea during your fasting window. Artificial sweeteners can potentially disrupt the fasting state and are best avoided. For longer or more advanced fasts, consulting a healthcare professional is strongly recommended, especially for those with underlying health conditions, to ensure safety and effectiveness.

Conclusion

For most individuals seeking to use fasting to reduce inflammation, shorter, more frequent protocols like the 16:8 method or occasional 24-hour fasts are generally the safest and most effective starting points. These intermittent fasting approaches leverage the body's natural metabolic processes to help reduce markers of chronic inflammation. While prolonged fasts of 48 hours or more show a more complex, and potentially temporary, pro-inflammatory response before benefits are seen post-refeeding, they should only be undertaken with medical supervision due to the higher risks involved. Combining any fasting protocol with a nutritious, anti-inflammatory diet is the most powerful strategy for achieving and sustaining long-term health benefits. For more in-depth, clinically reviewed information on the science of fasting, consult reputable sources like the National Institutes of Health.

Frequently Asked Questions

Yes, intermittent fasting, particularly methods involving fasting for 16-24 hours, has been shown to reduce inflammatory markers by promoting cellular repair and suppressing key inflammation pathways like the NLRP3 inflammasome.

Recent studies on prolonged fasting (48+ hours) have indicated a temporary increase in certain inflammatory markers, like CRP, during the fasting period. While this may be a transient, adaptive response, it could pose a risk for individuals with pre-existing conditions and should be approached with caution and medical supervision.

Fasting helps reduce inflammation primarily by forcing the body to switch from burning glucose to fat for energy. This metabolic shift triggers cellular processes like autophagy (cellular cleanup) and increases anti-inflammatory signaling molecules, like arachidonic acid, which inhibit key inflammatory pathways.

For most people, a time-restricted eating schedule like the 16:8 method is effective and safe for reducing inflammation. For more significant effects, a 24-hour fast once or twice a week may be considered, but it is important to progress gradually.

Yes. To maximize the anti-inflammatory benefits of fasting, it is recommended to pair your protocol with an anti-inflammatory diet rich in whole foods, fruits, vegetables, nuts, and healthy fats, while limiting processed foods and sugar.

No. Certain individuals, including pregnant women, those with a history of eating disorders, and people with type 1 diabetes, should avoid fasting. It is crucial to consult a healthcare provider before starting any fasting regimen, especially for those with chronic health conditions.

The increase in inflammatory markers like CRP during prolonged fasts is believed to be an acute physiological response that may be linked to tissue repair mechanisms. These markers typically decrease significantly after the fast, once the refeeding period begins.