An interventional study of Dietary Fasting in Fasting, sponsored by University of California, Davis. Recruiting at 1 site in United States. Open to participants aged 20 Years to 40 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-07-06.
Sponsored by University of California, Davis · Not applicable, Interventional, and Basic science
This is a clinical trial assessing the effects of fasting on the immune system in healthy adults. Immune profiling, gene expression profiling, and flow cytometry on peripheral blood mononuclear cells (PBMCs) will be performed and we hypothesize that a period of fasting will alter the immune system in healthy adults.
Dietary restriction (DR) is an intervention demonstrated to increase healthy lifespan in various model organisms including yeast, worms, mice, and rhesus monkeys (Lee et al., 2016, Fontana et al., 2015). It has been investigated extensively as a therapeutic modality in metabolic disease such as hypertension, cardiovascular disease, and obesity, with evidence of benefit independent of weight loss (Wilkinson et al., 2020, Zhu et al., 2020, Di Francesco et al., 2018). The major DR regimens include caloric restriction (CR) (Fontana et al., 2010), time-restricted feeding (TRF) (Brandhorst et al., 2015), fasting mimicking diets (FMD) (Mirzaei et al., 2014), and intermittent fasting (IF) (Chaix et al., 2014). Within the broader, poorly defined concept of IF, specific regimens exist that have yet to be standardized, including alternate-day fasting (ADF), 5:2 intermittent fasting (fasting 2 days per week), and daily TRF (typically restricting eating to an 8 hour window with 16 hours of fasting) (Chaix et al., 2014, Stekovic et al., 2019).
Studies of the effects of several different forms of DR on the immune system have shown both pro- and anti-inflammatory effects on immune responses, particularly with chronic calorie restriction (Choi et al., 2017). Certain periodic dietary restrictions prevent immune dysfunction and restore normal immune functioning by decreasing the number of circulating autoimmune cells from circulation and activating tissue regenerative capacity (Cheng et al., 2014). Although both chronic CR and nutrient-restricted FMD require substantial lifestyle modifications and can prove challenging in terms of adherence, forms of TRF and IF provide reasonable alternatives while showing similar efficacy. This makes forms of DR involving fasting rather than CR more appealing as a clinical intervention.
While multiple studies have shown positive effects on the immune system with various IF regimens in the setting of rheumatoid arthritis (Müller et al., 2001), multiple sclerosis, and cancer, mechanistic data in healthy humans are lacking. Recent studies have demonstrated changes in immune cell distribution with various regimens of CR and IF in murine models, supporting the exploration of potentially similar changes in healthy humans (Nagai et al. 2019). In order to study mechanistic details of the immune changes seen with DR in healthy humans, we designed this trial to examine the effects of fasting dose on multiple immune cell populations and relevant cell surface markers. While we observe a cohort over what is effectively only a single cycle of ADF, here we make an important step in characterizing the immune modulation occurring with ADF. This is one of the most studied fasting regimens, with substantial possibility for use as a clinical therapy in the future.
392 studies on the registry are indexed under Fasting; 63 are open to participants now.
This study's planned enrollment of 4 is below the median of 45 across 311 interventional studies indexed under Fasting.
Browse Fasting studies →University of California, Davis is the lead sponsor of 809 studies on the registry; 142 are open to participants now.
Of its 67 completed or terminated interventional studies of FDA-regulated products, 43 (64%) have results posted.
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Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
BMI (body mass index)
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Contraception
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Dietary fasting.
Behavioral: Dietary Fasting
The study will consist of two days of eating a "controlled habitual diet" and one 36-hour period of water-only fasting with glucose monitoring as a measure of compliance. Water intake will be limited to 2 liters/day to prevent electrolyte abnormalities. Subjects will undergo 4 separate blood-draws consisting of an overnight fasted sample (Baseline), a 2-hour postprandial sample (Fed), a 36-hour fasted sample (Fasted), and final 2-hour postprandial sample after the fasting period (Refed).
Changes in peripheral blood mononuclear cells
Changes in surface proteins and glycoproteins of peripheral blood mononuclear cells
Time frame: 7 months
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