Fasting for immunity: tiny study tests 36-Hour Water-Only fast

NCT ID NCT05104502

Knowledge-focused Sponsor: University of California, Davis Source: ClinicalTrials.gov ↗

First seen Jun 26, 2026 · Last updated Jul 07, 2026 · Updated 3 times

Summary

This study looks at how a 36-hour water-only fast changes immune cells in healthy young men. Four participants will have blood drawn before, during, and after fasting to measure immune markers. It's a very small, early-stage trial aimed at understanding, not treating, any condition.

What this could mean

Our plain-language read of the trial. This is informational only, not medical advice or a prediction.

Active substance: water-only fasting
What this could lead to: If successful, this could help scientists understand how fasting influences the immune system, potentially pointing toward dietary strategies for immune health.
What could go wrong: This is a very small, early study with only 4 participants, so results may not apply to the general population. It only looks at short-term changes, not long-term effects or benefits.

This is an AI summary of the original study and may miss details. Read our disclaimer.

Study facts

What this study's own registry entry says, in plain language.

Phase

Not a phased trial

Phase numbers describe drug development. The registry uses this when they do not apply, as it does for trials of devices, procedures or behaviour changes, and for observational studies.

Participants

About 4 people

The number the study aims to enrol. It can still change while the study runs.

Started

Mar 2022

Expected to finish

Sep 2026

An estimate. End dates often move.

Lead sponsor

Other sponsor

The registry's catch-all category, for sponsors it does not file as a company, a government agency, or a research network.

Who can take part

This study's own entry requirements. Only the study team can say for certain whether you qualify.

Ages

20 to 40 years

Sex

Anyone

Healthy volunteers

Accepted

You do not need to have the condition being studied to take part.

Show the full entry requirements

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: * Age: 20-40 years, to constitute a young study population * Gender: male subjects, to control for gender differences * BMI: 19-27 kg/m2 to constitute a normal/healthy weight population * Weight: 120 lbs or more * Fasting glucose: 70-100 mg/dL, to ensure that fasting can be tolerated without inducing dangerously low levels of blood glucose * Subjects must be willing to undergo a period of 36 hours of water-only fasting * Subjects must be willing to collect samples of each bowel movement produced throughout the entire study period for microbiome analysis * Subjects must be willing to collect blood pricks for blood glucose levels using a Contour Next One Blood Glucose Testing Kit during the fasting stage of the study protocol. Exclusion Criteria: * Current smoking * Anemia * Pregnancy or current breastfeeding * Chronic diseases including diabetes mellitus, thyroid disease, metabolic syndrome, cancer, or previous cardiovascular events * Gastrointestinal diseases including irritable bowel syndrome, Crohn's disease, ulcerative colitis, celiac disease * Consumption of \>1 alcoholic drink/day * Extreme dietary or exercise patterns * Recent weight fluctuations (greater than 10% in the last six months) * Regular use of over-the-counter allergy or pain medications (\>1/week) * Taking prescription lipid medications (e.g. statins) or other supplements known to alter lipoprotein metabolism such as isoflavones * Use of hormonal birth control including oral contraception pills, hormonal IUDs or rings, or hormonal birth control patches

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Conditions

The condition(s) this trial relates to.

Fasting

As listed by the trial registrant

The condition terms exactly as the trial's registrant entered them.

Fasting

How to take part

Only the study team decides who joins. These are the ways to reach them.

The places running it

1 site. The list below names each one and where it is.
The official record

ClinicalTrials.gov lists the study team's own contact details, including names and phone numbers. We don't republish those.

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A doctor treating you

A doctor who knows your case can contact a study site on your behalf, and can tell you whether this study is worth pursuing at all.

Fasting for immunity: tiny study tests 36-Hour Water-Only fast

What the study statuses mean