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

This study will evaluate the effectiveness of time-restricted eating (TRE), which is a form of intermittent fasting. When performing TRE, individuals consume all of their calories within a specific time window and then only consume water or other no calorie drinks the rest of the day. TRE is performed each day. There is no restriction on the quality or amount of food that people can consume during their eating window (ad libitum eating) with TRE, which can last anywhere from 4 to 12 hours. We are comparing three different 9-hour eating windows to determine whether the start and stop time of the eating window impact blood sugar control in individuals with obesity who also have or are at risk for type 2 diabetes. We also aim to determine if there are differences in the effects of the timing of eating window between males and females.

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.

Eligibility Criteria:
Inclusion Criteria:

* Aged \>18 years
* Body mass index \>30 kg/m2 and \<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 high (33+) Canadian Diabetes Risk Score)

Exclusion Criteria:

* Individuals with type 2 diabetes will be excluded if: (1) currently on \>3 monotherapies for diabetes, (2) have had diabetes therapy 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 \>5% in the last 3 months
  3. Taking antiobesity (weight loss) medications
  4. Body weight \>340lbs
  5. Diagnosed 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 eating during \<12 hour period on 5 or more days/week
  8. Physician-diagnosed eating disorder