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NCT Number: NCT07171281

Precise Eating Time to Improve Glycemic Control and Cardiometabolic Health in Prediabetes and Diabetes

The objective of this study is to investigate the impact of hypocaloric time-restricted eating (TRE) at different day times (early versus late TRE) on glucose metabolism and other cardiometabolic parameters in individuals with overweight and with normal, or impaired glucose metabolism (prediabetes and type 2 diabetes). In addition, the study aims to elucidate the molecular mechanisms underlying these effects.

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Key information

Conditions

PreDiabetes Behavior Body Weight Diabetes Mellitus Diabetes Mellitus, Type 2 Endocrine System Diseases Fasting Feeding Behavior Glucose Metabolism Disorders Intermittent Fasting Metabolic Diseases Nutrition Disorders Nutritional and Metabolic Diseases Obesity Obesity &Amp; Overweight Overnutrition Overweight Pathological Conditions, Signs and Symptoms Prediabetic State Signs and Symptoms Type 2 Diabetes

Age range

18 year–75 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

About this study

This dietary intervention study will follow a crossover design. During the intervention phases, participants will restrict their dietary intake to a defined eating window of 8 hours - predominantly in the morning (early TRE) or predominantly in the afternoon (late TRE) - in conjunction with a moderate caloric restriction for five weeks. A 10-12-week washout phase will separate the intervention periods.

Overweight and obese individuals with healthy glucose metabolism, prediabetes, or non-insulin-treated type 2 diabetes will be recruited for the study.

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Overweight or obesity (BMI 25-40 kg/m²)
  • Healthy glucose metabolism (fasting glucose <100 mg/dl and glucose after 2 hours OGTT <140 mg/dl)
  • OR impaired glucose metabolism (fasting glucose 100-125 mg/dl and/or glucose after 2 hours OGTT 140-199 mg/dl and/or HbA1c 5.7-6.4%)
  • OR type 2 diabetes (according to existing medical diagnosis or fasting glucose >126 mg/dl and/or glucose after 2 hours OGTT >200 mg/dl and/or HbA1c ≥6.5%)
  • Daily eating window ≥12 hours

Exclusion criteria

  • Weight changes > 5% within past 3 months
  • Shift work
  • Traveling across more than one time zone within one month prior to the study
  • Pregnancy and breastfeeding
  • Eating disorders, food intolerance/allergy to ingredients in the diet product, vegan diet, practicing time-restricted eating
  • Severe chronic illnesses or other conditions that are incompatible with the planned intervention and examination program (e.g. type 1 diabetes, recent cardiovascular event, malabsorption, cancer in the last two years, etc.)
  • Treatment with insulin, sulfonylureas, and GLP-1 receptor agonists, steroid use (oral, cutaneous, or parenteral), regular intake of melatonin, anticoagulation treatment that cannot be paused
  • Extreme early and extreme late chronotypes

Treatment and study plan

Early time-restricted eating

Behavioral

Participants will restrict their eating window (8 hours eating and 16 hours fasting per day) and caloric intake moderately.

During the early TRE intervention, participants will primarily consume their meals in the morning. The precise eating window will be defined based on the individual chronotype of the participants. Additionally, participants will be required to reduce their daily caloric consumption by 25%. They will replace one daily meal with a calorie-reduced product to facilitate caloric restriction.

Other names: eTRE, early TRE

Late time-restricted eating

Behavioral

Participants will restrict their eating window (8 hours eating and 16 hours fasting per day) and caloric intake moderately.

During the late TRE intervention, participants will primarily consume their meals in the evening. The precise eating window will be defined based on the individual chronotype of the participants. Additionally, participants will be required to reduce their daily caloric consumption by 25%. They will replace one daily meal with a calorie-reduced product to facilitate caloric restriction.

Other names: LateTRE, lTRE

Primary outcomes

  1. Mean 24-hour glucose

    Time frame: 5 weeks

    Mean 24-hour glucose assessed by continuous glucose monitoring (CGM)

Secondary outcomes

  1. Glycemic variability

    Time frame: 5 weeks

    Inter- and intraday indices of glycemic variability assessed by CGM

  2. Glucose levels

    Time frame: 5 weeks

    Fasting and postprandial glucose [mg/dL] in response to a mixed meal tolerance test

  3. Insulin levels

    Time frame: 5 weeks

    Fasting and postprandial insulin [mU/L] in response to a mixed meal tolerance test

  4. Glucagon levels

    Time frame: 5 weeks

    Fasting and postprandial glucagon [pmol/L] in response to a mixed meal tolerance test

  5. Insulin resistance

    Time frame: 5 weeks

    Insulin resistance, as assessed by HOMA-IR [AU]

  6. Insulin secretion

    Time frame: 5 weeks

    Insulin secretion, as assessed with the insulinogenic index [AU]

  7. Body weight

    Time frame: 5 weeks

    Body weight [kg], as measured by scale weight

  8. Body Mass Index (BMI)

    Time frame: 5 weeks

    BMI [kg/m2], calculated as weight/square height

  9. Waist and hip circumference

    Time frame: 5 weeks

    Waist and hip circumference [cm] measured by tape

  10. Body composition

    Time frame: 5 weeks

    Body fat mass and lean mass [kg], as measured by bioelectrical impendance analysis (BIA)

  11. Fasting cholesterol

    Time frame: 5 weeks

    Fasting total cholesterol, low-density lipoprotein and high-density lipoprotein cholesterol [mmol/L]

  12. Fasting triglycerides

    Time frame: 5 weeks

    Fasting triglycerides [mmol/L]

  13. Blood pressure

    Time frame: 5 weeks

    Systolic and diastolic blood pressure [mm Hg], as measured by manometer

  14. Resting energy expenditure

    Time frame: 5 weeks

    Resting energy expenditure [kcal/day], as assessed by indirect calorimetry

  15. Gene expresssion in adipose tissue

    Time frame: 5 weeks

    RNAseq analysis of subcutaneous adipose tissue samples

  16. Inflammatory markers in blood and adipose tissue

    Time frame: 5 weeks

    Levels of adipokines and inflammatory markers measured in blood samples and subcutaneous adipose tissue samples

  17. Subjective satiety and hunger sensation

    Time frame: 5 weeks

    Satiety and hunger scores assessed using Visual Analog Scales (VAS, with a scale of 1-100, where higher values correspond to stronger satiety/hunger)

  18. Concentration of satiety and hunger regulating hormones

    Time frame: 5 weeks

    Levels of ghrelin and peptide YY (PYY), as measured in blood samples in [pg/mL]

  19. Species and strain-level microbiome changes

    Time frame: 5 weeks

    Species and strain-level microbiome changes, as assessed by 16S rRNA gene sequencing of stool samples

  20. Levels of microbiome-derived metabolites

    Time frame: 5 weeks

    Levels of microbiome-derived metabolites measured in stool samples and blood plasma

  21. Sleep quality

    Time frame: 5 weeks

    Sleep quality as assessed by the Pittsburgh Sleep Quality Index (PSQI score, which ranges from 0-21, where higher values correspond to worse sleep quality) and also monitored by an ActiGraph device

  22. Sleep and wake timing

    Time frame: 5 weeks

    Sleep onset and offset assessed by the Pittsburgh Sleep Quality Index (PSQI score, which ranges from 0-21, where higher values correspond to worse sleep quality) and in addition by using a sleep diary

  23. Internal circadian phase

    Time frame: Screening visit (week 0)

    Internal circadian phase as assessed using the BodyTime assay in peripheral mononuclear blood cells (PBMCs)

  24. Glucagon-like peptide-1 levels

    Time frame: 5 weeks

    Fasting and postprandial glucagon-like peptide-1 (GLP-1) in response to a mixed meal tolerance test [pM]

  25. Gastric inhibitory polypeptide

    Time frame: 5 weeks

    Fasting and postprandial gastric inhibitory polypeptide (GIP) in response to a mixed meal tolerance test [pg/mL]

  26. Gene expresssion in peripheral mononuclear blood cells (PBMCs)

    Time frame: 5 weeks

    RNAseq analysis of clock, metabolic and inflammatory gene expression peripheral mononuclear blood cells (PBMCs)

  27. Malondialdehyde

    Time frame: 5 weeks

    Plasma malondialdehyde [µmol/L]

  28. 3-nitrotyrosine

    Time frame: 5 weeks

    Plasma 3-nitrotyrosine [pmol/mg]

  29. Protein carbonyls

    Time frame: 5 weeks

    Plasma protein carbonyls [nmol/mg]

  30. 36-item Short Form Health Survey (SF-36) to measure health-related quality-of-life

    Time frame: 5 weeks

    Health-related quality-of-life, as assessed by the 36-Item Short Form Health Survey (SF-36, with scores ranging from 0 to 100, with a higher score defining a more favorable health state)

  31. Satisfaction with the intervention

    Time frame: 5 weeks

    Satisfaction with the intervention assessed by a 5-point Likert scale (with 5 representing "Very satisfied" and 1 representing "Very dissatisfied")

  32. Decision behavior

    Time frame: 5 weeks

    Impulsiveness assessed by decision making tasks on computer

Other outcomes

  1. Physical activity level

    Time frame: 5 weeks

    24-h physical activity level (light, moderate, sedentary activity, metabolic equivalent of task) will be monitored by an Actigraph device

  2. Liver enzyme levels and renal values

    Time frame: 5 weeks

    γ-glutamyltransferase (GGT), aspartate aminotransferase (ALT), and alanine aminotransferase (AST), creatinine, urea, uric acid determined in fasting blood samples

  3. Food intake

    Time frame: 5 weeks

    Energy intake [kcal/day] assessed by food records

  4. Macronutrient intake

    Time frame: 5 weeks

    Percentage of calories from fat, carbohydrates, protein, and fiber, determined based on dietary records

  5. Food timing

    Time frame: 5 weeks

    Start and stop times of daily eating window and clock time of each daily meal intake assessed by food records

Study contacts

Contact information is provided by the study sponsor or research team.

Bettina Schuppelius, M.Sc.

CONTACT

[email protected]

+49 33200 882692

Olga Ramich, Prof. Dr.

CONTACT

[email protected]

+49 33200 882749

Sponsors and collaborators

Lead sponsor

German Institute of Human Nutrition

Other

Collaborators

  • German Center for Diabetes Research
  • Technische Universität Dresden
  • Technische Universität München, Germany
  • University of Geneva, Switzerland
  • University of Rovira i Virgili, Spain
  • University of Surrey, UK

Registry information

Official study title

Precise Eating Time to Improve Glycemic Control and Cardiometabolic Health in Prediabetes and Diabetes: the GLYCOTIME Trial

Acronym: GLYCOTIME

Important dates

Study start
2025
Primary completion
2027
Study completion
2028
First posted
Sep 12, 2025
Registry last updated
Sep 12, 2025

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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