The Impact of a 48-hour Fast with or Without Exercise on Immune Cell Metabolism and Glycemic Control in Healthy Active Adults

Participants will perform two, 48-hour fasts separated by 5 days while wearing a continuous glucose monitor to measure glycemic responses. The order of the trials will be randomized for each participant. The two trials will include an exercise condition (FAST+EX) and a control, non-exercise condition (FAST). During the FAST+EX trial, participants will perform 60 minutes of cycling on each of the two days of the fast. Each bout of exercise will be 60 minutes in duration and consist of 50 minutes of cycling at 60% of predicted heart rate reserve (HRR) followed by 5 x 1-minute intervals at 90% of predicted HRR with 1-minute of passive recovery between each interval. During the FAST trial, participants will be asked to refrain from any structured exercise during the days of the fast. To start the trial, participants will arrive at the lab following an overnight fast. They will consume a standardized meal replacement (Ensure Plus Calories) and blood will be drawn 2 hours post-ingestion. Participants will come to the lab 24 and 48 hours later for subsequent blood draws prior to breaking their fast with the same standardized meal replacement. Another blood sample will be taken 2 hours post-prandial. Participants will be asked to replicate food consumption in each condition for the 24-hour period after they break their fast, and consume the same standardized meal replacement on the morning following the completion of each fast to measure free-living glycemic control 24-hours after a fast performed with or without exercise. There will be a five-day wash out period in between the completion of both trials for all participants.

• Alteration in immune cell functions [Срок оценки: Baseline and 48 hours]
• Change in glucose tolerance [Срок оценки: Baseline, after 48 hours of fasting, and 24 hours after breaking the fast in free-living condition)]
• Blood pressure [Срок оценки: Baseline, 24 hours into the fast, and at the end of the fast (48 hours)]
• Rate and level of ketosis [Срок оценки: Baseline, 24 hours and 48 hours during fasting]
• Compensatory movement behaviour [Срок оценки: During and 48 hours after the fast]
• Hunger sensation [Срок оценки: At baseline, 12:00, 18:00 during the first and second day of the fast.]
• Sleep quality [Срок оценки: Baseline the morning before starting the fast, after 24 hours of fasting, and again after 48 hours of fasting.]
• Affect during exercise [Срок оценки: Before, during (e.g., at 10, 20, 30, 40, and 50 minutes as well as during intervals 1,2,3,4, and 5 at the end of the intervals as well as during the passive recovery) and following the two exercises conditions (post 5 minutes in a seated position).]
• Remembered Enjoyment [Срок оценки: 10 minutes after each exercise session.]
• Rate of perceived exertion [Срок оценки: During both exercise sessions at 10, 20, 30, 40, and 50 minutes as well as during intervals 1, 2, 3, 4, and 5 at the end of the intervals.]
• Glucose homeostasis [Срок оценки: During and 24 hours after both condition]