Effect of Low-calorie Diets With Different Macronutrient Composition and Macronutrient Distribution in Shift Workers With Prediabetes or Type 2 Diabetes and Overweight or Obesity.

Inclusion Criteria:

• Body mass index (BMI) ranging between 27.5 and 40 kg/m2.

• Presence of prediabetes (fasting glucose between 100-125 mg/dL and/or glycatedhemoglobin between 5.7 and 6.4%) or type 2 diabetes mellitus (fasting glucose ≥ 126mg/dL and/or glycated hemoglobin ≥ 6.5% and/or currently taking metformin), based onthe criteria of the American Diabetes Association.

• Engaged in shift work, including night shifts, for at least 1 year and intending tomaintain this schedule in the upcoming months.

• Provide written informed consent for voluntary participation in the study afterreviewing the participant information sheet and addressing any resulting queries.

Exclusion Criteria:

• Treatment with antidiabetic medications (oral or subcutaneous) or insulin in thelast 2 months, except for stable use of metformin or Dipeptidyl peptidase 4 (DPP-4)inhibitors for a minimum of 6 months.

• Treatment with lipid-lowering agents in an unstable manner for at least 6 monthsprior to study entry.

• Regular consumption of functional foods such as phytosterols or red yeast rice,which have a significant effect on lipid or glucose metabolism, in an unstablemanner for at least 6 months prior to study entry.

• Presence of other chronic conditions that are not well-controlled and couldinterfere with study outcomes, such as cardiovascular disease, renal disease, orliver disease.

• Presence of uncontrolled endocrine disorders, including hypothyroidism.

• Use of medications that could interfere with lipid and/or glucose metabolism, unlesstaken stably throughout the study.

• Consumption of sleep supplements, except for stable use for 6 months with theintention to continue stable use throughout the study.

• Presence of any laboratory abnormalities that could affect study results.

• Weight gain or loss of ≥ 5% in the last 3 months.

• Use of vitamin supplements in an unstable manner for at least 6 months prior tostudy entry.

• High intake of alcohol (> 30 g of ethanol) on a regular basis.

• Pregnancy or intention to become pregnant during the study.

• Severe illness of any kind with a life expectancy of less than 1 year or that, inthe investigators' judgment, limits uniform dietary intake throughout the study.

• Any other circumstance that, in the investigators' judgment, would impede adequateadherence to the proposed nutritional intervention (e.g., frequent travel during thestudy, inability to attend visits due to personal or work-related circumstances,etc.).