Intermittent Fasting Cut Long COVID Symptoms Nearly in Half in a New Randomized Trial: What the Research Shows

Intermittent Fasting Cut Long COVID Symptoms Nearly in Half in a New Randomized Trial: 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 wanted to know whether intermittent fasting could meaningfully reduce the persistent symptoms of Long COVID — fatigue, brain fog, joint and muscle pain, and other lingering effects that can last years after infection. This was the first randomized trial to directly compare two time-restricted eating approaches head-to-head in people living with Long COVID: a milder daily time-restricted eating (TRE) window against a more intensive multi-day fasting protocol.

The trial grew out of patient-led research, initiated by a Long COVID patient with a five-year history of symptoms, and was carried out with Pacific Northwest University of Health Sciences.

Who Was Studied

Participant profile: Adults with Long COVID, with a mean symptom duration of more than two years at the time they entered the study. Because this was a crossover design, every participant completed both the TRE phase and the fasting phase, in randomized order, separated by the study's structure rather than by being split into two separate permanent groups.

How the protocol worked in this study: After a 2-week run-in period on a no-sugar diet, participants were randomized to either the TRE phase or the fasting phase first, then crossed over to the other protocol for the remaining 4 weeks. The fasting phase used periodic 1–2 day fasts, with a median duration of 38 hours and a mean of 42 hours, structured as "night-day-night" fasts. The no-sugar diet was maintained as the dietary baseline throughout all 10 weeks.

What the Researchers Found

Overall Symptom Reduction

Across the full 10-week program — combining the no-sugar diet, TRE, and fasting — participants' overall Long COVID symptom score dropped by more than half.

Fasting vs. Time-Restricted Eating

• The multi-day fasting protocol outperformed the milder TRE protocol in reducing the LC-Score (p = 0.008)
• The number of reported Long COVID symptoms fell by −5.0 during the fasting phase, compared with −1.4 during the TRE phase (p = 0.002)
• This suggests that within this trial, the more intensive fasting protocol produced a larger symptom benefit than daily time-restricted eating alone

Safety

No major adverse safety events were recorded during either the TRE phase or the fasting phase.

What Did Not Change

• The study did not report data on lean muscle mass changes, as body composition was not a primary focus of this symptom-focused trial

What the Researchers Concluded

The researchers concluded that a 10-week program combining a no-sugar diet with intermittent fasting — and periodic multi-day fasting in particular — significantly reduced patient-reported Long COVID symptoms, with the more intensive fasting protocol outperforming milder daily time-restricted eating.

What This Means If You Fast

• This is early but genuinely promising evidence for a hard-to-treat condition. Long COVID currently has very few proven interventions, so a randomized trial showing a 51.8% reduction in symptom scores is a meaningful data point, not proof of a cure.
• The fasting protocol wasn't extreme. A median of 38 hours (roughly a night-day-night pattern) is a well-defined periodic fast, not prolonged starvation — similar in structure to protocols covered in what happens during a 36-hour fast.
• More intensive fasting outperformed milder time-restricted eating in this trial. That doesn't mean longer is automatically better for everyone — especially with a chronic illness — but it's a notable finding worth watching in future replication studies.
• Diet quality mattered throughout. The no-sugar diet was present in every phase of the study, so the results reflect fasting layered on top of a lower-sugar baseline, not fasting in isolation.
• Anyone with Long COVID considering this should loop in their doctor first, especially given the fatigue, post-exertional malaise, and metabolic sensitivity that can accompany the condition — this is exactly the kind of situation where starting fasting gently and building up matters most.

Study Limitations

• Moderate sample size (58 completers), typical for an early trial in a hard-to-recruit population
• Crossover design means order effects and carryover between phases can't be fully ruled out, even with randomization
• Symptom scores were patient-reported, which carries inherent subjectivity and recall bias
• No separate long-term follow-up reported beyond the 10-week study window
• The no-sugar diet was present throughout, making it difficult to fully separate the effect of fasting itself from the effect of reduced sugar intake
• Funding sources were not clearly reported in the available summaries of this study

Source

Bunker T, Horne BD, Baldwin MD, Sorrells R, Turner S, Laube L, Solomon A, Horne LA, Novack J. Intermittent fasting and a no-sugar diet for Long COVID symptoms: a randomized crossover trial. Scientific Reports. 2025;15:27563. PMID: 40730806

Frequently Asked Questions

Can intermittent fasting help with Long COVID symptoms?

In this 2025 randomized trial, a 10-week program combining a no-sugar diet with intermittent fasting reduced Long COVID symptom scores by 51.8%, with the more intensive multi-day fasting protocol producing a larger benefit than milder daily time-restricted eating.

How long were the fasts used in this Long COVID study?

Participants followed periodic 1–2 day fasts structured as "night-day-night," with a median duration of 38 hours and a mean of 42 hours, alternating with 4-week blocks of milder daily time-restricted eating.

Is fasting safe for people with Long COVID?

In this trial, no major adverse safety events were recorded during either the fasting phase or the time-restricted eating phase, but Long COVID involves significant fatigue and metabolic sensitivity in many patients, so anyone considering this should talk to their doctor first and start conservatively.

Did diet alone explain the improvement, or was fasting itself responsible?

Both groups followed the same no-sugar diet throughout the study, and the fasting phase produced significantly better results than the time-restricted eating phase on the same diet — suggesting the fasting protocol itself, not just the diet, contributed to the additional improvement.

How many people were in this Long COVID fasting study?

Sixty adults with Long COVID were randomized and 58 completed the full 10-week crossover trial, with an average symptom duration of more than two years at the start of the study.

Related Research and Articles

• What happens to your body during a 36-hour fast?
• How to start intermittent fasting
• Intermittent fasting and inflammation: what the research shows
• Does intermittent fasting help with brain fog?
• What is time-restricted eating?

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