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

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

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.

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.

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