Intermittent Fasting and a No-Sugar Diet for Long COVID Symptoms

April 22, 2026 updated by: Pacific Northwest University of Health Sciences

The Effect of a No-added Sugar Diet, Time-restricted Eating and Periodic Water Fasting on Long COVID Symptoms

This cross-over study will assess a no added sugar diet, a restricted daily eating window, and one or two full day water fasts to determine if there is an effect on self-reported symptoms of Long Covid (PASC).

Study Overview

Status

Status

Indicates the current recruitment status or the expanded access status.
Completed

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.

Detailed Description

This remote study will use a cross-over design to test a diet change plus a 10-12 hour eating window (Treatment A) compared to a diet change, an 8-hour eating window, and one 36 or 60 hour fast per week (Treatment B). Both potential Treatment A and potential Treatment B are 4 weeks in duration. To be eligible, subjects must have a minimum of five common long COVID-19 symptoms. The fasting will limit food intake but not water intake. There will be a two-week run-in with weekly surveys of patient-reported symptoms and severity. The subjects will be randomly assigned to Group AB or to Group BA. Since the water fasts are at the beginning of the week (with symptoms surveyed at the end of the week) there is a 5-6 day washout and then a cross-over to the other treatment for Group BA. A Likert 0-4 scale is used to track the severity of 28 of the most common patient-reported symptoms each week. An additional 30 symptoms are also tracked. Subjects are asked to follow a no-added sugar diet for the entire 10 weeks of the study.

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Interventional

Enrollment (Actual)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
77

Phase

Phase

The stage of a clinical trial studying a drug or biological product, based on definitions developed by the U.S. Food and Drug Administration (FDA). The phase is based on the study's objective, the number of participants, and other characteristics. There are five phases: Early Phase 1 (formerly listed as Phase 0), Phase 1, Phase 2, Phase 3, and Phase 4. Not Applicable is used to describe trials without FDA-defined phases, including trials of devices or behavioral interventions.
  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact

The name and contact information for the person who can answer enrollment questions for a clinical study. Each location where the study is being conducted may also have a specific contact, who may be better able to answer those questions.

Study Contact Backup

Study Locations

  • United States
    • Colorado
      • Boulder, Colorado, United States, 80303
        • Remote trial - anyone residing in the United States
    • Washington
      • Yakima, Washington, United States, 98901
        • Pacific Northwest University

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria

  • Adult (18-69 years old)
  • Five or more common Long Covid symptoms
  • Free from fever > 100F and known bacterial and parasitic infections
  • Must indicate willingness to limit certain supplements and report all medications.
  • Must indicate willingness to make significant dietary changes - and limit daily eating to an 8 or 10 hour window.
  • Must indicate willingness to attempt 36 hr or 60 hr water fasts each week for 4 weeks.
  • Have a valid email address and phone number
  • Reside in the United States
  • Be able to read and to communicate in English
  • Must indicate willingness to avoid "extra" supplements such as Fish Yes Oil, Cod liver Oil, Krill Oil, MCT oil, Coconut Oil, Tumeric/Curcumin, Berberine, Quercetin (> 500 mg), Red Yeast Rice, French Marine Bark extract, Red Sage, Ginko biloba, Oregano Oil, Peppermint Oil, Black seed oil, Cinnamon bark extract, Elderberry, Stinging Nettle, Milk Thistle, Monolaurin, Vendicinals 9, Tollovid, QuadraMune and all Probiotics.
  • Must indicate willingness to avoid certain nutraceuticals such as Zinc (more than 25 mg), Arginine, Glutamine, Palmitoylethanolamide (PEA), Alpha Lipoic Acid, L Carnitine and Taurine during the study period.
  • Must indicate willingness to avoid longevity supplements such as NAD+, Niacin, NMN, Nicotinamide Riboside, Spermidine and Fisetin during the study period.
  • Must indicate willingness to halt Olive oil consumption greater than 1 tsp daily during the study period.

Exclusion Criteria:

  • Likely COVID-19 or SARS-CoV-2 infection < 45 days before enrollment
  • Body Mass Index (BMI) must be 20 or greater
  • Past history of an eating disorder.
  • Previously fasted more than 18 hours with Long COVID
  • Currently doing intermittent fasting
  • Pregnant or breast-feeding
  • Severe pulmonary disease requiring supplemental oxygen
  • Partial loss of vision due to macular degeneration
  • Any recent (90 days) history of malignancies, fractures, surgery, radiation, chemo, anesthesia, or traumas
  • Diagnosed with Type I or Type II Diabetes
  • Previous Autoimmune condition
  • Heart condition (Coronary artery disease, Heart valve disease, Heart No failure, Stroke)
  • Pre-pandemic Arrythmia
  • Liver disease
  • Previous Chronic Health Conditions that did not fully resolve (Includes ME/CFS, Lyme Disease, and Fibromyalgia)
  • Prescription anticoagulation medication that cannot be halted during the study period. Brilinta (ticagrelor), Plavix (clopidogrel), Coumadin, Warfarin etc.
  • High Cholesterol medications that cannot be halted or reduced during the study period (Fenofibrate, Statins > 10 mg)
  • Anti-inflammatories or immunosuppressants such as Steroids, Low dose Naltrexone (LDN), Maraviroc, Remicade/Infliximab or Colchicine that cannot be halted during the study period
  • Metformin, Ivermectin, or peptides such as BCP-157 that cannot be halted during the study period

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: Randomized
  • Interventional Model: Crossover Assignment
  • Masking: Single

Arms and Interventions

Participant Group / Arm

Participant Group / Arm

A group or subgroup of participants in a clinical trial that receives a specific intervention/treatment, or no intervention, according to the trial's protocol.
Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.
Active Comparator: 10-12 hour daily Time-Restricted Eating (4 weeks)
In this crossover trial, half the participants did the 10-hour TRE first (treatment A), half did it last. A no added sugar diet was suggested for the entire study.
Other: Low sugar diet and 10-12 hour eating window
Low sugar diet and 10-12 hour eating window for four weeks
Experimental: 8-hour TRE, weekly 23 to 60 hour fast (4 weeks)
Eating in an 8-hour window daily, with one 23-60 hour fast per week. A no-added sugar diet was suggested.
Other: Low sugar diet, 8 hour eating window and fasting
Low sugar diet, 8 hour eating window and a 36-60 hour fast once per week for four weeks.

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Measure Description
Time Frame
Change in LC-Score, Per Treatment
Time Frame: Before and after 4 weeks of Fasting treatment or TRE treatment
This Outcome Measure is calculated by subtracting the Long COVID symptom severity score (LC-Score) before a treatment from the LC-Score after the treatment (i.e., score-after minus score-before). Negative values represent a reduction in number and severity of symptoms following treatment. LC-Scores are the sum of severity scores (0-4) for 28 common symptoms plus the count of 32 additional symptoms present. The maximum possible LC-Score is (28x4)+32 = 144.
Before and after 4 weeks of Fasting treatment or TRE treatment
Change in Number of Long COVID Symptoms, Per Treatment
Time Frame: Before and after 4 weeks of Fasting treatment or TRE treatment
This Outcome Measure is calculated by subtracting the Number of Long COVID symptoms (numLCsym) before a treatment from the numLCsym after the treatment (i.e., number-after minus number-before). Negative values represent a reduction in number of symptoms following treatment. The numLCsym is the count of 60 common symptoms.
Before and after 4 weeks of Fasting treatment or TRE treatment

Secondary Outcome Measures

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
Outcome Measure
Measure Description
Time Frame
Change in LC-Score, Overall
Time Frame: From enrollment to the end of the final treatment (10 weeks)
This Outcome Measure is calculated by subtracting the Long COVID symptom severity score (LC-Score) at baseline from the LC-Score after the final treatment (i.e., score-after minus score-before). Negative values represent a reduction in number and severity of symptoms following treatment. LC-Scores are the sum of severity scores (0-4) for 28 common symptoms plus the count of 32 additional symptoms present. The maximum possible LC-Score is (28x4)+32 = 144.
From enrollment to the end of the final treatment (10 weeks)
Change in Number of Long COVID Symptoms, Overall
Time Frame: From enrollment to the end of the final treatment (10 weeks)
This Outcome Measure is calculated by subtracting the Number of Long COVID symptoms (numLCsym) at baseline from the numLCsym after the final treatment (i.e., number-after minus number-before). Negative values represent a reduction in number of symptoms following treatment. The numLCsym is the count of 60 common symptoms.
From enrollment to the end of the final treatment (10 weeks)
Serious Adverse Events
Time Frame: During 4 weeks of Fasting treatment or during 6 weeks of TRE
Adverse events were medically reviewed and categorized as Serious if appropriate
During 4 weeks of Fasting treatment or during 6 weeks of TRE

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
Pacific Northwest University of Health Sciences

Investigators

Investigators

A researcher involved in a clinical study. Related terms include site principal investigator, site sub-investigator, study chair, study director, and study principal investigator.
  • Principal Investigator: Jeffrey Novack, PhD, Pacific northwest university of health sciences

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
November 4, 2022

Primary Completion (Actual)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
July 1, 2024

Study Completion (Actual)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
September 10, 2024

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
January 3, 2023

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
January 17, 2024

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
January 19, 2024

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
May 14, 2026

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
April 22, 2026

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
April 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant numbers.
  • 2022-06-PNWU

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

IPD Plan Description

No current plan to share data with other researchers.

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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