Fasting for Health: How long do you have to fast to get rid of inflammation?

October 12, 2025 •

3 min read

According to a 2024 study, a single 24-hour fast can increase levels of arachidonic acid, a lipid with anti-inflammatory properties. However, the answer to the question, "How long do you have to fast to get rid of inflammation?", is highly dependent on the fasting duration, with contrasting effects observed in short-term versus prolonged fasts.

Quick Summary

Short-term fasting can yield anti-inflammatory effects through cellular repair processes, but evidence shows that prolonged fasting (over 48 hours) can acutely and temporarily increase inflammatory markers. The most effective strategy for lasting anti-inflammatory benefits is a consistent healthy diet and safe fasting practices.

Key Points

Duration is Key: The inflammatory response to fasting differs significantly based on its duration; short-term fasting (12-24 hours) may reduce inflammation, while prolonged fasting (over 48 hours) can increase it temporarily.
Short-Term Benefits: Intermittent fasting (16-24 hours) promotes cellular repair through autophagy and increases anti-inflammatory compounds like arachidonic acid and ketone bodies.
Prolonged Risks: Fasting for multiple days (e.g., 10 days water-only) can cause a significant, though often transient, increase in pro-inflammatory markers like C-reactive protein (CRP) and IL-8, carrying risks for those with underlying conditions.
Focus on Diet Quality: A long-term, consistent anti-inflammatory diet, such as the Mediterranean diet, focused on whole foods, healthy fats, and fiber, is often a safer and more effective strategy for chronic inflammation than extreme fasting.
Refeeding Matters: The inflammatory spike from prolonged fasting often subsides after a controlled refeeding period, but this highlights the body’s initial stress response to extended nutrient deprivation.
Medical Guidance is Advised: Due to potential risks, especially with prolonged fasting, individuals with pre-existing conditions like heart disease or diabetes should seek medical advice before beginning any intensive fasting regimen.

The Science Behind Fasting and Inflammation

Fasting triggers metabolic and cellular changes that influence the body's inflammatory state. When deprived of food, the body switches to burning stored fat, producing ketone bodies, like beta-hydroxybutyrate (BHB), which have anti-inflammatory properties by inhibiting the NLRP3 inflammasome. Fasting also upregulates autophagy, a process that removes damaged cells and can reduce inflammation. Furthermore, fasting can improve gut health and blood sugar control, both linked to inflammatory response.

Intermittent Fasting (Short-Term): The Anti-Inflammatory Effects

Intermittent fasting, involving regular, shorter fasting windows (e.g., 12 to 24 hours), is generally associated with anti-inflammatory benefits. Studies show that fasting for this duration can decrease white blood cell levels, an inflammation indicator. Research, including a 2024 study on a 24-hour fast, highlights that restricting calories can increase arachidonic acid, a lipid that reduces NLRP3 inflammasome activity. Another study found that 16/8 intermittent fasting decreased pro-inflammatory cytokines like TNF-α and IL-6 over 21 days.

Prolonged Fasting (Over 48 Hours): The Surprising Pro-Inflammatory Response

Recent human studies indicate that prolonged fasting (48 hours or more) can increase systemic inflammation. A 2025 study on a 10-day water-only fast showed a pronounced increase in circulating inflammatory markers, including high-sensitivity C-reactive protein (hsCRP), ferritin, and interleukin-8 (IL-8). This acute pro-inflammatory response may be a temporary stress mechanism. While markers might return to baseline or drop after refeeding, the temporary spike during the fast carries risks, especially for individuals with pre-existing heart or vascular conditions.

Intermittent vs. Prolonged Fasting: A Comparison


Feature	Intermittent Fasting (e.g., 16/8)	Prolonged Fasting (e.g., >48 hours)
Duration	Typically 12-24 hours per cycle	Typically 2-10+ days
Primary Goal	Weight management, metabolic health, moderate anti-inflammatory effects	Deep ketosis, weight loss, cellular repair processes
Inflammatory Response	Generally associated with reduced inflammation and lower levels of markers like TNF-α and IL-6	Can cause a temporary increase in inflammatory markers like CRP and IL-8 during the fast
Key Mechanism	Upregulates autophagy and boosts anti-inflammatory compounds	Induces deep ketosis and metabolic shifts, but also triggers a temporary stress response
Safety & Risk	Considered relatively safe for most healthy adults	Carries higher risks and should be medically supervised, especially for individuals with health conditions

How to Support an Anti-Inflammatory Diet

For consistent and long-term anti-inflammatory benefits, focus on a diet rich in anti-inflammatory foods like the Mediterranean or DASH diets.

Anti-inflammatory foods to include:

Fruits and Vegetables: Berries, leafy greens, tomatoes, and oranges.
Healthy Fats: Olive oil, nuts, and seeds.
Fatty Fish: Salmon, mackerel, and sardines, rich in omega-3s.
Whole Grains and Legumes: Brown rice, oats, barley, beans, and lentils for fiber.
Herbs and Spices: Turmeric, ginger, and garlic.

Pro-inflammatory foods to limit:

Processed meats and refined carbohydrates.
Sugary drinks and sweets.
Excessive saturated and trans fats.

Other Factors Influencing Inflammation

Lifestyle factors beyond diet and fasting also play a role:

Physical Activity: Regular exercise helps control inflammation.
Weight Management: Maintaining a healthy weight is crucial, as excess fat contributes to chronic inflammation.
Sleep and Stress Management: Poor sleep and high stress can increase inflammatory markers.

Conclusion

The optimal fasting duration for inflammation is nuanced. Short-term intermittent fasting (12-24 hours) shows consistent anti-inflammatory benefits, while prolonged fasting (over 48 hours) can temporarily increase inflammatory markers. A combination of a regular anti-inflammatory diet and consistent, moderate intermittent fasting is generally the safest approach. Prolonged fasting requires strict medical supervision due to potential risks. For more information on anti-inflammatory diets, consult resources like the British Heart Foundation.

Frequently Asked Questions

Research suggests that fasting for at least 12 hours, and particularly 16-24 hours, can initiate metabolic changes like autophagy and increase anti-inflammatory compounds.

Recent studies, including a 2025 trial, indicate that prolonged water-only fasting (over 48 hours) can acutely increase inflammatory markers like C-reactive protein (CRP), though these may return to normal after refeeding.

While short, regular intermittent fasting tends to be beneficial, inconsistent or overly prolonged fasting can act as a stressor, potentially triggering a pro-inflammatory response in some individuals.

Fasting induces metabolic changes such as ketosis and autophagy, which regulate immune function, reduce inflammatory signals, and promote cellular repair to help manage chronic inflammation.

Yes, a ketogenic diet can be anti-inflammatory. By producing ketone bodies like beta-hydroxybutyrate (BHB), it mimics some of fasting's metabolic effects and has been shown to reduce inflammatory signals.

For most individuals, focusing on a healthy, anti-inflammatory diet while practicing consistent time-restricted eating (e.g., a 12-16 hour daily fast) is a safer approach than attempting prolonged fasts.

People with pre-existing conditions, including heart disease, diabetes, and a history of eating disorders, should avoid prolonged fasting without strict medical supervision.