Exercise Training and Vitamin D Metabolism (Hybri-D)

May 22, 2026 updated by: Dimitrios Draganidis, University of Thessaly

The Impact of Hybrid-type High-intensity Interval Training on Vitamin D Metabolism in Adults With Overweight/Obesity

The prevalence of Vitamin D deficiency is significantly higher in adults with overweight/obesity compared to those with normal body mass index (BMI). The "entrapment" of Vitamin D in adipose tissue due to impaired lipolytic stimulation and/or adipose tissue dysfunction has been proposed as the driving mechanism. Exercise training has been proposed as a promising strategy to increase mobilization of Vitamin D from adipose tissue, given its well described role in stimulating lipolysis. Indeed, a recent study revealed that participation in moderate-intensity cardiovascular type exercise over winter can mitigate the decline in 25-hydroxyvitamin D [25(OH)D] in adults with overweight/obesity, independent of weight loss. The aim of this study is to investigate the impact of hybrid-type high-intensity interval training over winter on vitamin D metabolism, in adults with overweight/obesity.

Study Overview

Status

Status

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

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

Thirty adults with overweight/obesity (both males and females) who will meet the inclusion criteria will be randomly assigned to either an Exercise group (n=15) or a Control group (n=15). The Exercise group will participate in three hybrid-type high-intensity interval training sessions per week over a 12-week period, while receiving a balanced diet. The Control group will receive a balanced diet but will not participate in exercise training. Both groups will provide a resting blood sample and undergo assessment of their body composition (via bioelectrical impedance analysis), daily dietary intake (via dietary recalls) and physical activity level (via accelerometry) at baseline (prior to intervention), 6 weeks and 12 weeks.

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 (Estimated)

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.
30

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

  • Name: Ioannis G Fatouros, PhD
  • Phone Number: 2431047047
  • Email: ifatouros@uth.gr

Study Locations

  • Greece
    • Karyes
      • Trikala, Karyes, Greece, 42100
        • Recruiting
        • Department of Physical Education and Sport Science, University of Thessaly
        • Contact:
        • Contact:
          • Athanasios Z Jamurtas, PhD
          • Phone Number: 2431047054
          • Email: ajamurt@uth.gr
        • Sub-Investigator:
          • Eytychia Giouvri, BSc

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

Accepts Healthy Volunteers

Yes

Description

Inclusion Criteria:

  • BMI = 25-35 kg/m2
  • Absence of musculoskeletal injuries
  • Absence of chronic health-related complications
  • Non-smokers

Exclusion Criteria:

  • Consumption of Vitamin D supplements
  • Consumption of anti-inflammatory drugs, statins and/or steroids

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: Other
  • Allocation: Randomized
  • Interventional Model: Parallel 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.
Experimental: Exercise group
Exercise group will participate in three hybrid-type high-intensity interval training sessions per week over a 12-week period, while receiving a balanced diet
Other: Exercise training
Receive a balanced diet and participate in three hybrid-type high-intensity interval training sessions per week over a 12-week period
Active Comparator: Control group
Control group will receive a balanced diet but will not participate in exercise training
Other: Control
Receive a balanced diet but abstain from any type of exercise training

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 calcium concentration
Time Frame: At baseline, 6 weeks and 12 weeks
Calcium concentration will be determined in serum
At baseline, 6 weeks and 12 weeks
Change in albumin concentration
Time Frame: At baseline, 6 weeks and 12 weeks
Albumin concentration will be determined in serum
At baseline, 6 weeks and 12 weeks
Change in 25-hydroxyvitamin D concentration
Time Frame: At baseline, 6 weeks and 12 weeks
25-OH-VD will be quantitatively determined in serum
At baseline, 6 weeks and 12 weeks
Change in plasma Vitamin D binding protein concentration
Time Frame: At baseline, 6 weeks and 12 weeks
Vitamin D binding protein concentration will be determined in plasma
At baseline, 6 weeks and 12 weeks
Change in aspartate aminotransferase (SGOT) concentration
Time Frame: At baseline, 6 weeks and 12 weeks
SGOT concentration will be determined in serum on a Clinical Chemistry analyzer
At baseline, 6 weeks and 12 weeks
Change in alanine aminotransferase (SGPT) concentration
Time Frame: At baseline, 6 weeks and 12 weeks
SGPT concentration will be determined in serum on a Clinical Chemistry analyzer
At baseline, 6 weeks and 12 weeks
Change in gamma-glutamyl transferase (γ-GT) concentration
Time Frame: At baseline, 6 weeks and 12 weeks
γ-GT concentration will be determined in serum on a Clinical Chemistry analyzer
At baseline, 6 weeks and 12 weeks

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 dietary intake
Time Frame: At baseline, 6 weeks and 12 weeks
Dietary intake habits will be assessed through dietary recalls
At baseline, 6 weeks and 12 weeks
Change in physical activity level
Time Frame: At baseline, 6 weeks and 12 weeks
Physical activity will be assessed via accelerometry
At baseline, 6 weeks and 12 weeks
Change in body composition
Time Frame: At baseline, 6 weeks and 12 weeks
Body composistion will be assessed via bioelectrical impedance analysis (BIA)
At baseline, 6 weeks and 12 weeks
Change in reduced glutathione concentration
Time Frame: At baseline, 6 weeks and 12 weeks
Reduced glutathione concentration will be determined in blood erythrocytes
At baseline, 6 weeks and 12 weeks
Change in oxidized glutathione concentration
Time Frame: At baseline, 6 weeks and 12 weeks
Oxidized glutathione concentration will be determined in blood erythrocytes
At baseline, 6 weeks and 12 weeks

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.
University of Thessaly

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: Dimitrios Draganidis, PhD, University of Thessaly

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 10, 2025

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.
January 31, 2026

Study Completion (Estimated)

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.
July 20, 2026

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).
December 9, 2025

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.
December 9, 2025

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.
December 23, 2025

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 26, 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.
May 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.
May 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.
  • UTH_2612_8.10.2025

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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