The CLOCK Study - A Human Dietary Intervention Study on Peripheral Circadian Clocks and Energy Metabolism (CLOCK)

August 20, 2025 updated by: Prof. Dr. med. Andreas F. H. Pfeiffer, German Institute of Human Nutrition

Interplay of Peripheral Circadian Clocks With Energy Balance and Body Weight Regulation

This human dietary intervention study with a cross-over design aims to investigate the effect of two different diurnal patterns of meal composition on peripheral circadian clocks and energy metabolism in healthy men.

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

In this cross-over study, healthy male participants are randomly allocated to one of two study groups: In study group (A) participants consume isocaloric carbohydrate-rich meals (65% Carbohydrates; 20% Fat; 15% Protein) in the morning and fat-rich meals (35% Carbohydrate; 50% Fat; 15% Protein) in the evening for four weeks. After a washout-phase participants consume isocaloric fat-rich meals in the morning and carbohydrate-rich meals in the evening for another four weeks. Study group (B) receives the same interventions in the reversed order.

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.
32

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 Locations

  • Germany
      • Potsdam, Germany, 14558
        • German Institute of Human Nutrition

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

18 years to 70 years (Adult, Older Adult)

Accepts Healthy Volunteers

Yes

Description

Inclusion Criteria:

  • BMI between 22 kg/m² and 34,9 kg/m²
  • Normal glucose tolerance determined in a 75g-oral glucose tolerance test
  • Impaired fasting glucose determined in a 75g-oral glucose tolerance test
  • Impaired glucose tolerance determined in a 75g-oral glucose tolerance test

Exclusion Criteria:

  • Shift workers or history of shift work
  • Men suffering from diseases or conditions that might influence the outcome of the study. Of special interest are diseases that influence body weight regulation (enteropathy, malabsorption, hepatopathy, renal disease, endocrine disorders, diabetes mellitus, eating disorders, heart disease etc.). Also men suffering from coagulopathy, apoplexy and myocardial infarction are excluded from the study.
  • Men suffering from psychiatric disease
  • Planned changes in physical activity during the study
  • Participation in other clinical studies within the last three months
  • Weight changes > 2 kg within 2 months prior to screening day
  • Men unable to give an informed consent
  • Men unable to engage in the dietary interventions
  • Men following a special diet

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: Basic Science
  • Allocation: Randomized
  • Interventional Model: Crossover Assignment
  • Masking: None (Open Label)

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.
Other: Carbohydrate-rich_Fat-rich (HC_HF)
Isocaloric carbohydrate-rich meals in the morning (06.00 am - 01.30 pm) and isocaloric fat-rich meals in the evening (04.30 pm - 10.00 pm) for 4 weeks
Other: Carbohydrate-rich (HC)
65% Carbohydrate; 20% Fat; 15% Protein
Other: Fat-rich (HF)
35% Carbohydrate; 50% Fat; 15% Protein
Other: Fat-rich_Carbohydrate-rich (HF_HC)
Isocaloric fat-rich meals in the morning (06.00 am - 01.30 pm) and isocaloric carbohydrate-rich meals in the evening (04.30 pm - 10.00 pm) for 4 weeks
Other: Carbohydrate-rich (HC)
65% Carbohydrate; 20% Fat; 15% Protein
Other: Fat-rich (HF)
35% Carbohydrate; 50% Fat; 15% Protein

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
Time Frame
Dietary-induced changes of glucose and lipid metabolism
Time Frame: week 4
week 4
Effect of different diurnal patterns of meal composition on peripheral circadian clocks in blood cells and subcutaneous adipose tissue
Time Frame: week 4
week 4

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
Dietary-induced changes of satiety and hunger scores
Time Frame: week 4
Measured via visual analogue scales
week 4
Effect of different diurnal patterns of meal composition on Lipopolysaccharide-induced cytokine expression
Time Frame: week 4
week 4
Dietary-induced changes of the human adipose tissue lipidome
Time Frame: week 4
week 4
Integrative analysis of dietary-induced changes of the human adipose tissue transcriptome
Time Frame: week 4
Microarray Analysis of adipose tissue samples
week 4

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.
German Institute of Human Nutrition

Collaborators

Collaborators

An organization other than the sponsor that provides support for a clinical study. This support may include activities related to funding, design, implementation, data analysis, or reporting.
Charite University, Berlin, Germany
German Federal Ministry of Education and Research
Heidelberg University
Max-Planck Institute of Molecular Cell Biology and Genetics

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.
  • Study Director: Andreas FH Pfeiffer, Prof. Dr., German Institute of Human Nutrition

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

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.
January 1, 2014

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, 2015

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.
August 1, 2015

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).
May 28, 2015

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.
June 30, 2015

First Posted (Estimated)

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.
July 1, 2015

Study Record Updates

Last Update Posted (Estimated)

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.
August 26, 2025

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.
August 20, 2025

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.
August 1, 2025

More Information

Terms related to this study

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.
  • DFG grant KFO218 PF164/16-1
  • DDG021023 (Other Grant/Funding Number: Deutsche Diabetes Gesellschaft)

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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