Periodic Fasting Linked to 61% Lower Risk of COVID-19 Hospitalization or Death: What the Research Shows

Medical disclaimer: This article summarises published research for informational purposes only. It is not medical advice and is not a substitute for guidance from a qualified health professional. Always consult your doctor before starting any fasting protocol, especially if you have an existing health condition or take medication.

Study at a Glance

What This Study Looked At

Researchers at Intermountain Health in Salt Lake City wanted to know whether people who practised long-term periodic fasting were protected against severe COVID-19 illness during the pre-vaccine era. The INSPIRE (INterventional Study In Patients Investigating ResEarch) registry had been enrolling patients who had coronary angiography at Intermountain Health since 1994. This gave researchers access to a well-characterised patient population that included a significant proportion of members of The Church of Jesus Christ of Latter-day Saints (LDS), many of whom practised monthly 24-hour water-only fasting as a religious observance — giving researchers a rare real-world group with decades of consistent fasting experience.

The study asked a timely question: did this long-term habit of periodic fasting make any difference when COVID-19 arrived? You can read more about how intermittent fasting affects immune function and fasting's effects on inflammation in related articles on this site.

Who Was Studied

Participant profile: All participants were enrolled in the INSPIRE registry — patients who had undergone coronary angiography at Intermountain Health between 2013 and 2020, and who subsequently tested positive for SARS-CoV-2 between March 2020 and February 2021. This is a predominantly older adult cohort with established cardiovascular risk (consistent with the coronary angiography inclusion criterion). A larger secondary cohort of 1,524 INSPIRE patients with any COVID-19 test result was also analysed.

How periodic fasting worked in this study: Participants in the fasting group had been practising a monthly 24-hour water-only fast — typically on the first Sunday of each month, as is common LDS religious practice — for an average of 40.4 ± 20.6 years prior to COVID-19 diagnosis. This is not a study of an imposed fasting intervention; it captures the real-world outcomes of decades-long consistent fasting habit in a cohort of cardiovascular patients.

What the Researchers Found

Primary Outcome: Hospitalization or Mortality

The primary outcome was the composite of all-cause hospitalization or all-cause mortality following COVID-19 diagnosis.

• The composite outcome of hospitalization or death occurred in 11.0% of periodic fasters versus 28.8% of non-fasters (p = 0.013)
• Hazard ratio: 0.61 (95% CI: 0.42 to 0.90) — periodic fasters had 39% lower relative hazard of the composite outcome
• This association remained after adjusting for age, sex, and cardiovascular risk factors in the primary analysis

Secondary Cohort Findings (n=1,524)

Among the broader cohort of 1,524 INSPIRE registry participants with any SARS-CoV-2 test result, those who practised periodic fasting also showed lower rates of COVID-19-related adverse outcomes, further supporting the primary cohort finding.

Duration of Fasting Practice

A notably striking finding was the length of fasting experience in the fasting group: an average of 40.4 years (±20.6 years) of monthly 24-hour fasting before COVID-19 arrived. This is not a population that recently adopted fasting — these are long-term, lifelong practitioners.

What Did Not Change

• Infection rates (being COVID-positive vs negative) showed a trend favouring fasters in the secondary cohort, but this was not the primary outcome measure
• The study was not designed to measure immune biomarkers, inflammatory markers, or viral load — so mechanistic immune data was not collected
• The study could not separate fasting effects from other LDS health practices (abstinence from alcohol, tobacco, and caffeine)

What the Researchers Concluded

Horne and colleagues concluded that routine periodic fasting was associated with significantly lower risk of hospitalization or mortality among COVID-19 patients during the pre-vaccine era, and that periodic fasting "may be a complementary therapy to vaccination that could provide immune support and hyperinflammation control during and beyond the pandemic."

What This Means If You Fast

• Long-term fasting habits appear to confer immune resilience. The fasting group in this study had practised monthly 24-hour fasting for an average of four decades. This is not a benefit you acquire in a week — it's the product of years of consistent practice.
• The protection was substantial. An 11% vs 28.8% hospitalization or death rate is a 2.6-fold difference in outcomes. Even accounting for healthy lifestyle factors co-occurring with LDS fasting practice, this magnitude of difference is clinically meaningful.
• The mechanism likely involves immune regulation. Research on fasting and immune function shows that periodic fasting reduces inflammatory cytokines (IL-1β, IL-6, TNF-α) and activates cellular clean-up processes (autophagy) that help the body respond to infection without the hyperinflammatory "cytokine storm" that caused many severe COVID-19 outcomes.
• Fasting may work partly through reducing chronic inflammation. Patients in the INSPIRE registry had established cardiovascular disease risk. Chronic inflammation is a key driver of both cardiovascular disease and COVID-19 severity. Long-term periodic fasting appears to reduce this baseline inflammatory load — making the body more resilient when infection occurs. Read more about how fasting reduces inflammation.
• This supports a long-term approach to fasting, not a short-term fix. The benefit was seen in people who had been fasting consistently for decades. This reinforces the case for making fasting a sustainable lifestyle practice rather than an occasional experiment.
• Autophagy is a plausible mechanism. Fasting activates autophagy — the cellular recycling process that clears damaged proteins and pathogens. Autophagy during fasting may help the immune system process viral threats more efficiently, potentially reducing the severity of infection once it occurs.

Study Limitations

• Observational design, not an RCT — causation cannot be established. Confounding factors may explain part or all of the association
• Healthy user bias — LDS church members who fast also typically abstain from alcohol, tobacco, and caffeine, and may have other healthier lifestyle factors. These were not all fully controlled for
• Single healthcare system — Intermountain Health is a large Utah system. The patient population is predominantly white, North American, and LDS, which limits generalizability to other populations
• Self-reported fasting status — the study relied on reported fasting practice, not verified through biomarkers
• No immune or inflammatory data collected — the mechanism behind the association was not measured
• Pre-vaccine era only — findings may not apply in the same way to vaccinated individuals or newer COVID variants
• Cardiovascular patient population — all participants had undergone coronary angiography, making this a higher-risk population than the general public
• Small primary cohort — n=205 (73 fasters) is sufficient to detect a large effect but may not capture more subtle differences

Source

Horne BD, Muhlestein JB, May HT, Le VT, Bair TL, Knowlton KU, Anderson JL; INSPIRE Registry Investigators. (2022). Association of periodic fasting with lower severity of COVID-19 outcomes in the SARS-CoV-2 prevaccine era: an observational cohort from the INSPIRE registry. BMJ Nutrition, Prevention & Health, 5(2):145–153. DOI: 10.1136/bmjnph-2022-000462. View on PubMed Central →

Frequently Asked Questions

Can intermittent fasting really protect you from COVID-19?

This study found that people with decades of periodic fasting experience had a 61% lower hazard of COVID-19 hospitalization or death during the pre-vaccine era. This is an observational association, not a clinical recommendation — but the magnitude and consistency of the finding is notable. The mechanism likely involves reduced baseline inflammation and enhanced cellular immune function through autophagy.

What type of fasting did the study participants do?

Participants practised a monthly 24-hour water-only fast, consistent with LDS (Latter-day Saint) religious practice. On average, they had done this for 40.4 years prior to COVID-19. This is periodic fasting — one 24-hour fast per month — not daily intermittent fasting or time-restricted eating.

Does daily intermittent fasting provide the same benefits as monthly fasting?

This study only examined monthly periodic fasting. Daily intermittent fasting has been studied for immune function separately — including a 2012 Ramadan study showing that 30 days of daily fasting significantly reduced IL-1β (−78%), IL-6 (−57%), and TNF-α (−66%). The immune benefits of fasting appear to be consistent across different protocols, with the key variable being consistency over time.

Why might fasting reduce COVID-19 severity?

Several mechanisms are plausible: (1) fasting reduces baseline inflammatory cytokines that contribute to COVID-19's "cytokine storm"; (2) fasting activates autophagy — cellular clean-up that may help clear viral particles and damaged cells; (3) fasting reduces insulin resistance and obesity, both of which are major risk factors for severe COVID-19; (4) fasting supports immune cell quality by triggering regeneration of immune cell populations during the refeeding period.

Should I start fasting specifically to protect against respiratory infections?

This study provides interesting evidence of an association between long-term fasting and lower COVID-19 severity, but it's not strong enough to be a clinical recommendation for infection prevention. The benefits in this study came from decades of consistent practice. Starting fasting for its general health benefits — metabolic health, inflammation reduction, weight management — is well supported by evidence. Immune resilience may be an additional long-term benefit of that consistent practice.

Related Research and Articles

• Research: Ramadan fasting significantly reduces IL-1β, IL-6, and TNF-α in 50 adults
• Research: Intermittent fasting and inflammation — network meta-analysis of 21 studies
• Research: Prolonged fasting regenerates the immune system — pilot human study
• Research: Alternate day fasting activates autophagy and improves aging biomarkers
• Does intermittent fasting reduce inflammation?
• How intermittent fasting promotes autophagy
• Intermittent fasting and inflammation: the research explained

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