What this trial measures

• Sleep onsetFrom enrollment to the end of baseline (2 weeks)

  Actigraphy determined sleep onset time (h:m)

• Sleep offsetFrom enrollment to the end of baseline (2 weeks)

  Actigraphy determined sleep offset time (h:m)

• Sleep DurationFrom enrollment to the end of baseline (2 weeks)

  Formula: sleep offset - sleep onset (h:m). A larger number indicates a longer sleep duration.

• M10From enrollment to the end of baseline (2 weeks)

  Average activity level from 10 hours of highest activity (counts/hour)

• L5From enrollment to the end of baseline (2 weeks)

  Average activity level from 5 hours of lowest activity (counts/hour)

• Relative AmplitudeFrom enrollment to the end of baseline (2 weeks)

  Formula: Relative Amplitude =(M10-L5)/(M10+L5). A value near 1 indicates a strong, well-defined circadian rhythm (high activity during the day and very low activity at night), and a value near 0 indicates a fragmented or "flat" rhythm (little difference between your most active and least active periods).

• Interdaily StabilityFrom enrollment to the end of baseline (2 weeks)

  The ratio of the variance of the average 24-hour activity profile to the variance of the overall 24-hour data. Actigraphy is collected over 2 weeks and averaged to create a single, representative 24-hour profile. Interdaily Stability values range from 0 to 1, where 0 indicates a total lack of stability and 1 indicates perfect stability. Lower values suggest fragmented, weak, or disrupted circadian rhythms.

• Caloric intake timingFrom enrollment to the end of baseline (2 weeks)

  Time of calorie consumption (h:m)

• MEQ ScoreBaseline measure in week 2

  The Morningness-Eveningness Questionnaire (MEQ) is a 19-item self-report assessment used to determine an individual's circadian preference (chronotype), ranging from morning-type to evening-type. Scores range from 16 to 86, with higher scores indicating morningness and lower scores indicating eveningness.

• PHQ9 ScoreBaseline measure in week 2

  The PHQ-9 is a 9-item, self-report questionnaire used to screen for and measure the severity of depression in clinical trials. It covers the 9 diagnostic criteria for major depressive disorder based on the DSM-IV. Total scores range from 0 to 27, with higher scores indicating higher levels of depression.

• PDQ-D5 ScoreBaseline measure in week 2

  The PDQ-D5 is a self-report questionnaire assessing subjective cognitive impairment. It includes five items covering four subscales: Attention/Concentration, Retrospective Memory, Prospective Memory, and Planning/Organization. The total score is the sum of the five items, ranging from 0 to 20. Higher scores indicate greater perceived cognitive deficits, while lower scores indicate fewer problems.

• PSQI ScoreBaseline measure in week 2

  The Pittsburgh Sleep Quality Index (PSQI) is a 19-item self-report questionnaire assessing sleep quality and disturbances over a one-month interval. It measures seven components (quality, latency, duration, efficiency, disturbances, medication, dysfunction) to produce a global score from 0 to 21, where higher scores indicate poorer sleep quality.

• Recruitment RateFrom study initiation to end of recruitment period (approximately 16 months)

  Formula: Total participants enrolled / enrollment time window, with higher numbers indicating better recruitment.

• Retention RateFrom enrollment to study completion (approximately 19 months)

  Formula: (number of participants that complete the study / number of participants that enrolled) x 100, reported as percentage with higher numbers indicating higher retention.

• Missing Data RateFrom baseline to end of study visit (weeks 1-12)

  The missing data rate is defined as the percentage of expected data points for primary outcomes (e.g., daily food logs, daily actigraphy wearing, and survey responses) that were not collected or were unusable at the final study visit. Calculation: (Number of missing data points / Total number of expected data points across all enrolled participants) × 100 reported as a percentage with higher values indicating more missing data. Note: This includes data missing due to participant withdrawal or non-response to specific survey items.

• Change in Mediterranean Diet Adherence Screener (13-MEDAS) ScoreMeasured at baseline in week 2 and during intervention in week 10

  Adherence to the Mediterranean Diet is assessed using the validated 13-item Mediterranean Diet Adherence Screener (13-MEDAS). The questionnaire evaluates the consumption frequency of Mediterranean dietary staples (e.g., olive oil, vegetables, fruits, nuts, fish, legumes) and frequency of unhealthy food choices (e.g., animal fats, sugar-sweetened beverages). Each item is scored 0 or 1. The total score ranges from 0 to 13, with higher scores indicating greater adherence.

• Time-restricted eating adherenceMeasured throughout nutritional intervention (week 3-11)

  Using the time of first and last caloric intake of the day, time-restricted eating adherence is calculated as the percentage of days where all food was consumed within the designated 10 h time window.

• Mediterranean Diet Intervention AcceptabilityEnd of study (week 10-12)

  Participant-reported manageability of diet changes on study team generated Intervention Acceptability Survey. A single item ("The Mediterranean diet changes were manageable") will be scored on a 5-point Likert scale (1 = Strongly Disagree, 5 = Strongly Agree). Data for all participants reported. Higher values indicate diet content modifications were more manageable.

• Time-Restricted Eating Intervention AcceptabilityEnd of study (week 10-12)

  Participant-reported manageability of diet changes on study team generated Intervention Acceptability Survey. A single item ("The time restriction on calorie intake was manageable") will be scored on a 5-point Likert scale (1 = Strongly Disagree, 5 = Strongly Agree). Data reported for Group 2 only (Mediterranean Diet + Time-Restricted Eating). Higher values indicate diet timing modifications were more manageable.

• Participant-Reported Global Impression of Change in DepressionEnd of study (week 10-12)

  A single-item assessment of the overall change in depression since study entry. Scale: 1 = Very Much Worse, 2 = Much Worse, 3 = Minimally Worse, 4 = No Change, 5 = Minimally Improved, 6 = Much Improved, 7 = Very Much Improved. Higher scores indicate greater improvement.

• Perceived Impact of Dietary Changes on SleepEnd of study (week 10-12)

  A single item ("The dietary changes made during the study had a positive impact on my sleep") will be scored on a 5-point Likert scale (1 = Strongly Disagree, 5 = Strongly Agree). Higher scores indicate a more positive perceived impact.

• Perceived Impact of Dietary Changes on Metabolic HealthEnd of study (week 10-12)

  A single item ("The dietary changes made during the study had a positive impact on my metabolic health") will be scored on a 5-point Likert scale (1 = Strongly Disagree, 5 = Strongly Agree). Higher scores indicate a more positive perceived impact.

• Perceived Impact of Dietary Changes on Overall HealthEnd of study (week 10-12)

  A single item ("The dietary changes made during the study had a positive impact on my overall health") will be scored on a 5-point Likert scale (1 = Strongly Disagree, 5 = Strongly Agree). Higher scores indicate a more positive perceived impact.

• Participant-Reported Intent for Long-term Dietary MaintenanceEnd of study (week 10-12)

  A single-item assessment of the participant's intention to continue the intervention diet after the study concludes ('I plan to maintain dietary changes from the study moving forward') will be scored on a 5-point Likert scale (1 = Strongly Disagree, 5 = Strongly Agree). Higher scores indicate a higher intent to maintain the dietary changes.