Time-restricted Eating, Window Timing, Type 2 Diabetes Status and Sex on Glycemic Control

The overarching aim of this study is to evaluate the interactions between TRE window timing, type 2 diabetes status, and sex among individuals with obesity. The first objective is to compare the effects of three 9-h TRE window times (early: 7:00-16:00 h, mid: 9:30-18:30 h, delayed: 12:00-21:00 h) on real-time, free-living glycemic control. The second objective is to determine if type 2 diabetes status (type 2 diabetes versus prediabetes or moderate+ risk for type 2 diabetes aka at risk for type 2 diabetes) modifies the effect of eating window timing on glycemic control outcomes. The exploratory objectives include: 1) determine whether sex modifies TRE adherence or the effect of TRE on metabolic changes relative to control; and 2) to compare changes in dietary intake, body weight, and blood pressure within and between early, mid, and delayed TRE. We have the following hypotheses related to these objectives:

1. The early TRE window will result in the most favourable glycemic control outcomes but also the lowest participant acceptability followed by mid and delayed TRE.
2. There will be larger differences in glycemic control outcomes between the TRE window timings among those with type 2 diabetes compared to those at risk for type 2 diabetes.
3. TRE adherence and changes in glycemic control, and weight loss with all TRE window times (relative to control) will be higher in men vs women.
4. Energy, carbohydrate, and sugar intake, body weight, and blood pressure will decrease during TRE, but with no differences by window timing.

• Early (7:00 - 16:00) TRE (Behavioral): A standardized TRE Protocol where participants eat ad libitum between the hours of 7:00 to 16:00 for 7 days. On the 8th day, they will consume a meal replacement beverage at 7:00, and not consume anything else for two hours.
• Mid (9:30 - 18:30) TRE (Behavioral): A standardized TRE Protocol where participants eat ad libitum between the hours of 9:30 to 18:30 for 7 days. On the 8th day, they will consume a meal replacement beverage at 9:30, and not consume anything else for two hours.
• Late (12:00 - 21:00) TRE (Behavioral): A standardized TRE Protocol where participants eat ad libitum between the hours of 12:00 to 21:00 for 7 days. On the 8th day, they will consume a meal replacement beverage at 12:00, and not consume anything else for two hours.

Primary outcomes

• Average 24-hour glucose total area under the curve (AUC) over 7 days [7 days]: Assessed for 7 continuous days using a continuous glucose monitor.

Secondary outcomes

• Average 24-hour glucose over 7 days [7 days]: Assessed for 7 continuous days using a continuous glucose monitor.
• Average daily nocturnal glucose over 7 evenings [7 days]: Assessed for 7 continuous evenings based on the sleep period identified by the Fitbit tracker using a continuous glucose monitor.
• Average daily time spent in hyperglycemia over 7 days [7 days]: The average number of hours with glucose >10 mmol/L over 7 continuous days assessed with a continuous glucose monitor.
• Postprandial glucose [2 hours]: Assessed on the morning after the 7th day of each TRE protocol. Participants will consume a standardized breakfast at a specified time, and glucose will be evaluated via continuous glucose monitor from the time they start consuming the breakfast for 2 hours.
• Glycemic viability [7 days]: The average of each standard metrics of glycemic viability (standard deviation, coefficient of variation, mean amplitude of glycemic exercise, and continuous overall net glycemic action) will be calculated over 7 continuous days from continuous glucose monitors.
• Patient acceptability [7 days]: Patient acceptability will be assessed based on researcher-developed questions related to their experience with each TRE protocol.
• TRE fasting duration adherence [7 days]: Participants will receive twice daily text messages asking what time they started and stopped eating that day, which will be used to calculate the length of the fast each day. Adherence will be calculated as the % of days where the participant fasted for 15h or longer.
• TRE fasting window adherence [7 days]: The proportion of days where participants began and ended their meal within 15 min or 30 min of their prescribed time.

Other outcomes

• Dietary intake [7 days]: Participants will complete the ASA-24 at baseline, and during each of the intervention periods to assess changes in macro and micronutrient composition of their diet.
• Weight change [7 days]: Participants will be asked to weigh themselves first thing in the morning, with minimal and no clothing on, after they have emptied their bowels once during the baseline period and on the last day of each of the intervention period.
• Blood pressure change [7 days]: Participants will be asked to measure their blood pressure once during the baseline period, and on the last day of each intervention period.
• Physical Activity [7 days]: Participants will be asked to wear a Fitbit for the duration of the study. We will average the amount of physical activity over 7 days of wear.
• Sleep [7 days]: Participants will be asked to wear a Fitbit for the duration of the study. We will average the amount of sleep over 7 days of wear.
• Safety and Adverse Events [7 days]: Participants will be given access to a questionnaire to report any symptoms throughout the intervention. We will compare the proportion of individuals who report these symptoms within each time period.

Sex: All, ages: 40 Years to any

Inclusion Criteria:

* Aged 40 years or older
* Body mass index <50 kg/m2
* Have access to an Apple or Android cellphone with Bluetooth.
* Have type 2 diabetes or be at risk for type 2 diabetes (defined as self-report of pre-diabetes, a recent (within 12 months) measure of HbA1c between 5.7 and 6.4%, waist circumference (WC) that is BMI specific; for women: BMI >= 18.5-24.9, WC >= 80cm; BMI >= 25-29.9, WC >= 90cm; BMI >= 30-34.9, WC >= 105cm; BMI >= 35+, WC >= 115cm; for men: BMI >= 18.5-24.9, WC >= 90cm; BMI >= 25-29.9, WC >= 100cm; BMI >= 30-34.9, WC >= 110cm; BMI >= 35+, WC >= 125cm.

Exclusion Criteria:

* Individuals with type 2 diabetes will be excluded if: (1) currently on >2 monotherapies for diabetes, (2) have had diabetes therapy medication or dosage changes <3 months, (3) self-reported hemoglobin A1c >9.0%, (4) taking exogenous insulin, or (5) taking sulfonylureas
* The following exclusion criteria applies to all potential participants:

  1. History of or referral for bariatric surgery
  2. Weight loss >3% in the last 3 months
  3. Taking antiobesity (weight loss) medications
  4. Body weight >390lbs
  5. Diagnosed with severe cognitive disorder that precludes them from giving consent
  6. Inability or unwillingness to change their eating window to follow those prescribed in the study
  7. Currently consistently eating during <11.5 hour period .
  8. Physician-diagnosed eating disorder
  9. Having a pacemaker or receiving dialysis.
  10. Not having access to a Lifelabs location.

• Amy A. Kirkham, PhD, Principal investigator, University of Toronto