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Diabetes Mellitus, Type 2NCT04155619

Using Early Time Restricted Feeding and Timed Light Therapy to Improve Glycemic Control in Adults With Type 2 Diabetes

A study testing No change in meal timing, No change in light exposure and Early Time-Restricted Feeding in people with Diabetes Mellitus, Type 2 and Time Restricted Feeding, run by University of Alabama at Birmingham at 1 site in United States.

Completed

Finished. The study has ended and is not enrolling. Results may be posted on the official record.

Official record
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Trial summary

The purpose of this study is to test whether eating earlier in the day and/or timed light therapy can improve blood sugar in people with type 2 diabetes. This study will also test whether these treatments improve other aspects of health, including the circadian (biological) clock, sleep, weight, body composition… Read more about this study

Who is it for?
Ages 30 to 80 years
What is being tested?
No change in meal timing, No change in light exposure and Early Time-Restricted Feeding
Could I receive a placebo?
No, everyone receives an active treatment
How many people
190 participants
Where
1 siteUnited States
Study dates
26 Apr 2021to 30 Apr 2026
Phase
Interventional
Are there results?
None posted in the registry

Key requirements

Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.

  • Ages 30 to 80 years
  • All sexes
  • No healthy volunteers
  • Adult, Older adult

Who may be able to join

  • Aged 30-80 years old
  • Have type 2 diabetes
  • HbA1c between 5.7 - 12.0%
  • On a stable dose of metformin, DPP-IV inhibitors, SGLT2 inhibitors, sulfonylureas, and/or GLP-1 receptor agonists for at least 6 weeks, or taking no diabetes medications
  • Wake up at a regular time between 5-9 am

Who cannot join

  • On insulin or diabetes medication other than metformin, DPP-IV inhibitors, SGLT2 inhibitors, sulfonylureas, and/or GLP-1 receptor agonists
  • Have type 1 diabetes or was diagnosed with diabetes before age 18
  • Moderate or severe retinopathy or other medical condition that may affect the ability to safely receive bright light therapy
  • A history of severe hypoglycemia
  • Change in the dosage of a chronic medication within the past month (need to wait at least 1 month prior to baseline visit)
  • Have a clinically significant laboratory abnormality (e.g., abnormal hemoglobin levels)
Show all 19Show fewer
  • Severe gastrointestinal disease, major gastrointestinal surgery, or active gallstone disease
  • Cardiovascular, renal, cardiac, liver, lung, adrenal, or nervous system disease that is unstable or may compromise study validity
  • Evidence of cancer (other than non-melanoma skin cancer) within the last 5 years
  • Pregnant or breastfeeding
  • Current diagnosis of a major psychiatric condition that would impair study participation
  • Diagnosed sleep disorder or circadian disorder that is not stabilized (sleep apnea is allowed). Those with narcolepsy will not be included.
  • Major changes in health or medical history in the last 3 months that could affect data validity per judgement of the study physician
  • Spend an average of more than 1.5 hours/day outdoors
  • Perform overnight shift work more than 1 day/week on average
  • Regularly eat within a less than a 10-hour period daily
  • Regularly finish eating dinner before 6:30 pm
  • Lost or gained more than 8 lbs within the last 2 months and weight needs to be stable for a minimum of 4 weeks before baseline testing
  • Traveled more than two times zones away in the two months prior to enrolling in the trial or will travel more than two time zones away during the 16-week study

Trial locations and contacts

1 site in 1 country.

United States1 site

  • University of Alabama at Birmingham; Birmingham Veterans Affairs Medical Center

    Birmingham, Alabama, 35294

Other trials in United States

About this study

The purpose of this study is to test whether eating earlier in the day and/or timed light therapy can improve blood sugar in people with type 2 diabetes. This study will also test whether these treatments improve other aspects of health, including the circadian (biological) clock, sleep, weight, body composition, cardiovascular health, quality of life, and mood.

Read the detailed description

The circadian system is strongly linked to type 2 diabetes. Adults with type 2 diabetes have circadian rhythms that are both weakened and mistimed. Weak rhythms may be due to insufficient bright light exposure during the daytime, irregular meal timing, or grazing on food throughout the day. Mistiming may be due to ill-timed food intake or light exposure-such as eating later in the day or light exposure at night-which causes central and peripheral circadian clocks within the body to become out of sync (circadian misalignment). This circadian misalignment impairs glucose metabolism: data now show that eating late in the day and light exposure at night rapidly elevate glucose (blood sugar) and insulin levels in humans within days. Conversely, well-timed food intake and light exposure appear to improve glycemic (blood sugar) control, circadian rhythms, and several other aspects of health.

This study will test the health effects of eating early in the daytime (early time-restricted feeding; early TRF) and timed light therapy in adults with type 2 diabetes. The study will test the following aims:

  1. Determine whether early TRF and/or timed light therapy improve glycemic control
  2. (a) Determine how early TRF and/or timed light therapy affect the central and peripheral circadian clocks and (b) determine which patients benefit the most from circadian-based therapies
  3. Determine whether early TRF and/or timed light therapy improve sleep, body weight, body composition, cardiovascular risk factors, quality of life, and psychological health.

Approximately 344 veterans and civilians aged 30-80 with insulin-independent type 2 diabetes will be randomized to the following 2 x 2 study design:

  1. No change in eating or light exposure habits
  2. Early TRF
  3. Timed light therapy
  4. Early TRF and timed light therapy

Participants will be asked to follow their assigned treatment for 16 weeks and then be followed up for an additional eight months (1 year in total). Baseline and post-intervention testing will be conducted during a 38-hour inpatient (hospital) stay. Testing will involve three 3-hour meal tolerance tests to determine insulin sensitivity and secretion; 24-hour measurement of glucose, insulin, and C-peptide levels; 24-hour measurement of cortisol and melatonin to measure the phase and amplitude of the central clock; and a constant glucose infusion to determine the phase and amplitude of the effective glycemic ("peripheral") circadian clock. Sleep, weight loss, body composition, and cardiovascular risk factors will also be measured, and questionnaires and an interview will be administered to determine improvements in quality of life and psychological health.

Note: Pre-registered primary and secondary outcomes are listed below. Pre-registered tertiary outcomes appear in the study protocol, which will be uploaded to this website.

Being tested
No change in meal timing, No change in light exposure, Early Time-Restricted Feeding, Timed Light Therapy
Medical subject headings
Diabetes Mellitus, Type 2, Intermittent Fasting

What participants receive

What participants receive. In a randomised study each person is assigned to one group by chance.

  • No change in meal timingBehavioural

    Participants will eat within an ≥11-hour daily period (no change in meal timing habits).

  • No change in light exposureBehavioural

    Participants will not change their light exposure habits.

  • Early Time-Restricted FeedingBehavioural

    Also called eTRF, early TRF

    Participants will eat within an 8-hour daily period early in the day, starting within 2 hours of waking up.

  • Timed Light TherapyBehavioural

    Also called Bright Light Therapy

    Participants will use bright light therapy for 60 minutes between 6 am - 3 pm, blue light-blocking glasses for one hour before bedtime, and blackout curtains at night.

Study groups in NCT04155619
Study groupRoleWhat they receive
No change in eating or light exposure habitsActive comparatorNot described
Receives: Behavioral: No change in meal timing; Behavioral: No change in light exposure
Early Time-Restricted FeedingExperimentalNot described
Receives: Behavioral: No change in light exposure; Behavioral: Early Time-Restricted Feeding
Timed Light TherapyExperimentalNot described
Receives: Behavioral: No change in meal timing; Behavioral: Timed Light Therapy
Early Time-Restricted Feeding and Timed Light TherapyExperimentalNot described
Receives: Behavioral: Early Time-Restricted Feeding; Behavioral: Timed Light Therapy

What is being measured

The primary outcome is the main question the study is designed to answer.

  1. 24-hour glucose levels

    Time-weighted mean, fasting, peak, standard deviation, and excursion (maximum - minimum) values (mg/dl)

    Measured: 16 weeks

  2. 24-hour insulin levels

    Time-weighted mean, fasting, peak, standard deviation, and excursion values (mU/l)

    Measured: 16 weeks

  3. 24-hour C-peptide levels

    Time-weighted mean, fasting, peak, standard deviation, and excursion values (pmol/l). This is also a proxy for total 24-hour insulin secretion.

    Measured: 16 weeks

  4. Hemoglobin A1C

    %

    Measured: 16 weeks

  5. Insulin sensitivity

    Insulin sensitivity (dl/kg/min/μU/ml) during three identical meal tolerance tests, as measured by the Oral Minimal Model. The individual, mean, and excursion values, and time of the peak value will also be calculated.

    Measured: 16 weeks

  6. Beta-cell responsivity index (a measure of beta-cell function)

    Beta-cell responsivity during three identical meal tolerance tests, as measured by the Oral Minimal Model. The individual, mean, and excursion values, and time of the peak value will also be calculated.

    Measured: 16 weeks

  7. Insulin secretion

    Insulin secretion (mU) across three identical meal tolerance tests, as measured by the Oral Minimal Model. The individual, mean, and excursion values, and time of the peak value will also be calculated.

    Measured: 16 weeks

Secondary outcomes (6)

  1. Melatonin Amplitude

    Peak value (pg/mL)

    Measured: 16 weeks

  2. Cortisol Amplitude

    Amplitude (μg/dl)

    Measured: 16 weeks

  3. Melatonin Phase

    Clock time of dim light melatonin onset (DLMO)

    Measured: 16 weeks

  4. Cortisol Phase

    Clock time of cortisol phase

    Measured: 16 weeks

  5. Glycemic ("Peripheral") Rhythm Amplitude

    Amplitude or diurnal variation in glucose levels (mg/dl) during a constant glucose infusion procedure

    Measured: 16 weeks

  6. Glycemic ("Peripheral") Rhythm Phase

    Time of day that glucose levels experience a nadir during a constant glucose infusion procedure

    Measured: 16 weeks

Timeline

From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.

  1. First posted7 Nov 2019
  2. Study start26 Apr 2021
  3. Primary completion30 Apr 2026
  4. Study completion30 Apr 2026

Resources

More details

For doctors and researchers: how the study is designed, who runs it, and its registry IDs.

Study design
Study type
Interventional
Phase
Phase N/A
Primary purpose
Treatment
Allocation
Randomised
Intervention model
Parallel groups
Masking
Single blind
Who is masked
Investigator
Enrolment
190 participants (actual)
IDs, dates and publications
ClinicalTrials.gov ID
NCT04155619
Sponsor's protocol ID
IRB-300003964
Other IDs
W81XWH-19-1-0558
Status last verified
May 2026
First submitted
5 Nov 2019
Last updated
2 Jun 2026
Results posted
No
Data monitoring committee
Yes
FDA-regulated drug
No
FDA-regulated device
No
Individual data sharing
Yes

Publications

  • Steger FL, Salvy SJ, Vaughan TB, Lowry C, Richman JS, Gamble KL, Garvey WT, Scheer FAJL, Peterson CM. Protocol for the CLOCKS study: A 4-arm randomized controlled trial testing the independent and combined effects of 2 chronotherapies-early time-restricted eating and daytime bright light therapy-in adults with type 2 diabetes. Nutr Res. 2026 Jul 17;153:142-159. doi: 10.1016/j.nutres.2026.07.006. Online ahead of print.

    PubMed 42594524

Questions about this trial

What is this clinical trial studying?

A study testing No change in meal timing, No change in light exposure and Early Time-Restricted Feeding in people with Diabetes Mellitus, Type 2 and Time Restricted Feeding, run by University of Alabama at Birmingham at 1 site in United States.

The full registered description is in the About this study section and the official record.

Who may be eligible to take part?

The sponsor lists 5 inclusion and 19 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.

Is this clinical trial currently recruiting?

The record says: finished, as of the sponsor's last update on 2 Jun 2026. Status can change between updates, so confirm with the study contact before making plans.

Where is the study taking place?

The record lists 1 site in United States. Whether a site is taking part right now should be confirmed with that site. See every site.

What are the possible benefits and risks?

They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.

Are results available for this study?

The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.

How can a doctor refer a patient or contact the research team?

The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.

What does the primary outcome measure?

24-hour glucose levels (time frame: 16 weeks). The study lists 7 primary outcomes in all. It is what the study was designed to measure, not a finding.

Where can I read the original study information?

On the ClinicalTrials.gov record for NCT04155619, which also lists 1 linked publication.

Does a listing mean the treatment is approved or proven to work?

No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.

How often is this information updated?

AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 2 Jun 2026.

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