Effects of HIIT vs. TRE on Type 2 Diabetes Risk

The 4-week HIIT intervention will use a stationary bicycle performed 3 times/week (a total of 12 sessions over the 4-week), performing at the CRL. All participants will perform a 20-minute HIIT protocol (20 repetitions of 10-seconds work time followed by 50-seconds resting/active recovery for the first two weeks, and 10 repetitions of 20-seconds work time followed by 100-seonds resting/active recovery for the rest of two weeks; targeted 90% HRmax) after 5-minute warm-up (10% HRmax). The supervisor (PI: Joon Young Kim and/or Graduate researcher: Wonhee Cho) will provide encouragement and supervision for exercise adherence. Heart rate (Polar, Polar Electro Oy, Kempele, Finland) and rating of perceived exertion (RPE; detail described in the questionnaire section) will be recorded.

Participants randomized into the TRE group will be instructed to consume all their calories within a 10-hour period. We will instruct participants that they can choose their time-window (early TRE \[7am - 5pm\] or late TRE \[1pm - 11pm\]), but it must remain constant for the duration of the study. Further, we will give no restrictions on the type of foods and/or the quantities individuals can consume. We will ask individuals to maintain their diet for the duration of the study. Participants will be given clear instructions on their diet and how to use the "MyFitnessPal" application. Participants will have their total daily energy requirement calculated using the following formula (Basal metabolic rate \[BMR\] x activity level) and will be told to eat that amount within their allotted time window. BMR will be calculated when participants have their body composition taken by the InBody. Participants will be told to start their 4-week diet the following day after visit.