Exercise-meal Timing and Postprandial Glucose Control
Condition: Diabetes Mellitus, Type 2; Hyperglycemia, Postprandial; Physical Activity; Glucose Intolerance
MeSH terms: Diabetes Mellitus, Type 2; Hyperglycemia; Glucose Intolerance
Study type: Interventional

Summary: 
      Physical activity helps maintain optimal postprandial blood glucose control. However, there
      is a lack of clear information regarding the optimal meal-activity timing required to
      maximize blood glucose control. By using continuous glucose monitoring (CGM), this randomized
      controlled trial will determine whether implementing a bout of physical activity immediately
      before, or immediately after, or shortly after a meal is most optimal. This study will also
      independently examine the effects of three different physical activities: walking, standing,
      and circuit-exercises. Minimizing the changes in blood glucose following a meal not only
      reduces the risk of type 2 diabetes but also reduces cardiovascular-related mortality.
      Therefore, the data produced by this project will have very important implications for
      informing healthcare policy and physical activity recommendations.
    

Detailed description: 
      Healthy volunteers will undergo an informed consent and screening visit to determine their
      eligibility. Participants who are included will then be assigned to one of the three studies
      (walking, standing, or circuit-exercises) and then come to the lab on 5 consecutive mornings
      to undergo a pre-trial visit and 4 experimental trial visits (A, B, C, and D). The order of
      the experimental trial visits will be randomized in a counter-balanced, cross-over design.

      Screening visit: Having read the participant info sheet, a study investigator will discuss
      the project with the potential participant who will have the chance to ask any questions.
      Informed consent will be sought and a General Health and Physical Activity Questionnaire will
      be completed. Body weight, height, resting heart rate, blood pressure, and waist
      circumference will be measured, and blood measures of glycated hemoglobin, triglycerides, and
      cholesterol will be taken.

      Pre-trials visit: Participants will come to the laboratory to receive an accelerometer
      physical activity monitor, a continuous glucose monitor, and to complete a physical activity
      bout (walking, standing, or stair climbing, depending on which study they are enrolled). Over
      the next 5 consecutive days, participants will be instructed to maintain their normal diet
      and activity habits, to record their dietary intake, to refrain from vigorous exercise and
      alcohol, and continue wearing the accelerometer and continuous glucose monitoring devices at
      all times.

      Experimental trial A: Following an 8-10 hour overnight fast, participants will come to the
      lab and will be given a 500 calorie meal-replacement drink to consume within 10 minutes. They
      will remain in a seated position for 2 hours and then complete the physical activity bout
      (30-min walk, 30-min stand, or 10-min circuit-exercises) after which they may leave the lab.
      Resting and post-activity heart rate and blood pressure will be recorded.

      Experimental trial B: Following an 8-10 hour overnight fast, participants will come to the
      lab and complete the physical activity bout. Immediately after this they will be given a 500
      calorie meal-replacement drink to consume within 10 minutes and will remain in a seated
      position for 2 hours, after which they may leave the lab. Resting and post-activity heart
      rate and blood pressure will be recorded.

      Experimental trial C: Following an 8-10 hour overnight fast, participants will come to the
      lab and will be given a 500 calorie meal-replacement drink to consume within 10 minutes.
      Immediately after finishing the meal they will complete the physical activity bout and then
      remain in a seated position until 2-hours has passed since ingesting the meal. After this
      time they may leave the lab. Resting and post-activity heart rate and blood pressure will be
      recorded.

      Experimental trial D: Following an 8-10 hour overnight fast, participants will come to the
      lab and will be given a 500 calorie meal-replacement drink to consume within 10 minutes.
      Thirty minutes after finishing the meal they will complete the physical activity bout and
      then remain in a seated position until 2-hours has passed since ingesting the meal. After
      this time they may leave the lab. Resting and post-activity heart rate and blood pressure
      will be recorded.

      After the final trial, the accelerometer and continuous glucose monitoring devices will be
      collected and the participant's role in the study will end.
    

Intervention name(s): Physical activity; Meal
Intervention type(s): Behavioral; Dietary Supplement
Intervention description(s): Physical activity will consist of either 30-mins of standing still, 30-mins of walking at a self-selected brisk pace on a treadmill, or 3-sets of circuit-exercises (10 squats, 10 push-ups, 10 lunges, 10 sit-ups).; Liquid meal replacement shake containing 500 kcal, with 55% kcals from carb, 30% from fat, and 15% from protein.
Allocation: Randomized
Intervention model: Crossover Assignment
Intervention model description: Three independent groups of participants will enter 1 of 3 studies, each of which involves a randomised, crossover, controlled trial containing 4 trials: (i) control, meal ingestion no activity; (ii) activity bout immediately prior to meal; (iii) activity bout immediately after ingestion of meal; (iv) activity bout 30-mins after ingestion of meal.
Masking: Single (Outcomes Assessor)
Primary purpose: Basic Science
Keywords: Exercise; Type 2 diabetes; Walking; Standing; Circuit exercises; Inactivity; Blood glucose control; Continuous glucose monitoring