Actively Recruiting
Uncovering the Impact of Diet on the Human Circadian Timing System
Led by Oregon Health and Science University · Updated on 2025-11-10
14
Participants Needed
1
Research Sites
N/A
Total Duration
On this page
Sponsors
O
Oregon Health and Science University
Lead Sponsor
N
National Institutes of Health (NIH)
Collaborating Sponsor
AI-Summary
What this Trial Is About
Researchers are investigating how diet affects the human circadian timing system, which is essential for regulating biological processes and overall health in sync with the 24-hour light-dark cycle. This study focuses on how quickly the body's internal clock adjusts or entrains when exposed to a high-fat diet, based on evidence from animal studies showing that high-fat diets can disrupt circadian rhythms. The trial aims to better understand these effects in healthy adults aged 18 to 40. The study uses a 46-day randomized crossover design with two diet interventions: a high-fat diet (50% fat, 35% carbohydrates, 15% protein) and a low-fat diet (30% fat, 55% carbohydrates, 15% protein). Participants will complete two inpatient visits of nine days each, separated by outpatient periods. During outpatient phases, they will follow strict sleep schedules and consume provided meals. In the inpatient phase, participants stay in controlled rooms without time cues while undergoing detailed monitoring including sleep studies, body temperature measurements, blood sampling, and metabolic assessments. Participants will maintain consistent sleep schedules verified by sleep logs and actigraphy before each inpatient visit. Researchers will monitor circadian phase changes, metabolic health markers, cognitive function, and mood over 18 days of diet exposure. The study includes 24-hour supervision by medical staff and continuous data collection to assess how diet influences circadian entrainment speed and related physiological outcomes. Total participation spans approximately 46 days with detailed health and behavior assessments throughout.
CONDITIONS
Brief Title
Food and Circadian Timing
Who Can Participate
Eligibility Criteria
You may qualify if you...
- Healthy, lean men and women
- Aged between 18 and 40 years
- Able to follow strict sleep-wake schedules and dietary plans
- Willing to avoid drugs, alcohol, nicotine, and caffeine during study periods
- Able to maintain consistent sleep schedules verified by actigraphy and logs
You will not qualify if you...
- Major dietary restrictions such as entirely dairy-free or meat-free diets
- Body mass index (BMI) outside 18.5 to 24.9 kg/m2 or waist circumference greater than 94 cm for men or 80 cm for women
- Psychiatric or psychological conditions unsuitable for participation
- Use of drugs, alcohol, or smoking
- Use of prescribed or over-the-counter medications
- History of irregular shift work or night work in the past year
- Travel across more than one time zone in the past three months
- Currently consuming a habitual high-fat diet
- Chronobiologic or sleep disorders
- Cardiovascular diseases
- Metabolic syndrome or related risk factors such as high cholesterol, blood pressure, blood glucose, or triglycerides
- Pre-diabetes or diabetes
- Hypertension
- Respiratory, kidney, urinary, gastrointestinal, immune, hematopoietic, neoplastic, endocrine, metabolic, or neurologic disorders
- Participation in another research study that could affect safe participation in this trial
AI-Screening
AI-Powered Screening
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Your Study Journey
Duration - 2 to 4 weeks
Participants are screened for eligibility to participate in the trial.
1 visit (in-person)
Duration - 14 days
Participants consume a controlled isocaloric diet, either high-fat or low-fat, for 14 days while maintaining a consistent 8-hour sleep schedule verified by actigraphy and sleep logs. Meals are either delivered or picked up approximately 3 times during this period.
Approximately 3 visits (in-person or meal delivery)
Duration - 9 days
Participants are admitted to a laboratory setting without external time cues for detailed physiological monitoring including polysomnography, core body temperature measurement, and blood sampling. This includes a constant posture protocol, a 6-day light-dark cycle change, and a second constant posture protocol.
Continuous inpatient stay with 24-hour monitoring
Duration - 14 days
Participants consume the alternate controlled isocaloric diet, either low-fat or high-fat, for 14 days while maintaining the consistent sleep schedule verified by actigraphy and sleep logs. Meals are either delivered or picked up approximately 3 times during this period.
Approximately 3 visits (in-person or meal delivery)
Duration - 9 days
Participants undergo a second inpatient stay identical to the first, with detailed physiological monitoring under controlled conditions to assess the effects of the alternate diet on circadian timing and metabolism.
Continuous inpatient stay with 24-hour monitoring
Trial Site Locations
Total: 1 location
1
Oregon Health & Science University
Portland, Oregon, United States, 97239
Actively Recruiting
Research Team
A
Andrew McHill, PhD
How is the study designed?
Study Type
INTERVENTIONAL
Masking
NONE
Allocation
RANDOMIZED
Model
CROSSOVER
Primary Purpose
OTHER
Number of Arms
2
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