Improving glucose monitoring with lifestyle intervention for individuals with impaired glucose tolerance

This study will utilise a within subject (cross-over) design and each 3 day intervention period will be separated by a minimum one week washout period. Each participant will undertake four separate experimental trials: (1) a series of low glycemic index (GI) meals (2) a series of high glycemic meals (3) low intensity intermittent training (LIT) and (4) high intensity interval training (HIT). A description of the dietary and exercise interventions are provided below. Continuous glucose monitor: The glucose sensor (Medtronic EnliteTM) will be inserted on the side of the torso under the skin 24 h prior to each experimental trial. The device will remain in situ for 72 hours and is water proof and does not prevent bathing or swimming activities. This will be repeated for each of the four experimental trials. Insertion of the microdialysis fibre into the superficial subcutaneous adipose tissue does not require anaesthetic, is minimally invasive and barely discernible. The glucose sensor measures interstitial glucose concentration and is connected to the digital recorder (Medtronic iProTM2). They are both secured to the skin surface by medical adhesive dressing (3MTM Tegaderm) and require no further intervention until removed. Dietary Intervention: All meals and snacks will be provided during each 12 h experimental trial. The low and high GI diets will be matched for carbohydrate (60%), protein (10-15%) and fat (25-30%) content but will differ in the glycemic index. The glycemic index of breakfast, lunch and dinner of the low and high GI diet will differ by ~40, 40 and 10 U, respectively. Breakfast, lunch and dinner will each be separated by 5 h and consumed at ~0730, 1230 and 1730 h during each experimental trial. Exercise Intervention: All meals and snacks from the high GI diet trial will be provided during each exercise trial. The two exercise sessions will be performed on separate occasions and will be matched for total mechanical work but will differ in the exercise intensity and duration. The LIT protocol will involve 3 x 15 minute bouts of cycling performed at 40% peak power output (PPO). One 15 minute bout of exercise will be undertaken prior to each meal (5 h recovery period between exercise bouts). The HIT protocol will involve a 5 minute warm up and 12 × 60 s repetitions of cycling at 80% PPO, each interspersed with 60 s active recovery at 40% PPO. The single HIT session will be undertaken before the first meal (breakfast) during the experimental trial. All exercise will be performed on a stationary indoor cycle ergometer. Heart rate (HR) and rating of perceived exertion (RPE) will be measured during exercise. Blood samples will be taken at rest prior to commencing the experimental trial, and at regular intervals throughout the day. Blood will be extracted via a catheter placed into a forearm vein.