Effect of lactose vs sucrose after exercise on postprandial blood glucose control.

Design. The design will be a double-blind, block randomized (Williams design), cross over design (lactose, sucrose, placebo) conducted over 3 months per participant, comprising of 3 trials and 10 visits to the laboratory. This consists of three 2-day trials per participant, 1 day baseline testing one week prior to experimental trials and insertion of continuous glucose monitor the day before each trial begins. Visit 1, 1. Study introduction, discussion, questions, consent. Laboratory and cycle ergometer familiarization with a short 3-5 min low intensity ride after bike fit. Visit 2, will consist of body composition measurements in order to determine body mass and body fat percentage as well as, VO2max/Wmax test and familiarization trial of the performance test. During all exercise sessions, participants will breathe through an on-line gas analysis facemask that covers the mouth and nose, and is attached to a 0.2 micro filter system, which filters microorganisms. At other times, participants will need to comply with the University's health recommendations regarding the global pandemic at the time. Visit 3, will be conducted at the laboratory either around 24 hours before experimental trial at 16:00 to 17:00h. At this time, a continuous glucose monitor (CGM) (Medtronics Guardian Connect) will be inserted into the subcutaneous tissue on back of the upper arm or if more suitable, on the outer upper thigh. Participants will remain in the lab for ~2-h while a calibration routine involving finger-prick blood samples is conducted (3 samples, time 0, 30 min, 2 h after placement). Participants in the meantime will be instructed on the calibration and data recording procedures using the Ipad or Android App, and also be instructing on the feeding protocol for the standardized diet that will be provided to participants to consume over the following 2-day metabolic trial. Visit 4, Day 1 of the metabolic trial. This day follows Visit 3. In the morning prior to breakfast, participants will conduct a calibration procedure of the CGM under video instruction from the researchers (Zoom, Teams, Skype). Participants will be free living and consume a standardized mixed-macronutrient meal at standarised times; 9:00 h (breakfast), 12:00 h (lunch) and 15:00 h (snack); depending on personal schedule, the meal and exercise times on both Day 1 and Day 2 may be moved back or forward 1 h. Participants will report to the laboratory at 17:00h with exercise-suitable clothing. After changing the CGM will be recalibrated. Next, they will perform a supervised session of high intensity interval exercise (10x1-min cycle intervals at 80% maximal power, with 1 min recovery at 30% maximal power, total 20 min). Post-exercise (5 min), the test drink or placebo will be ingested. The lactose and sucrose will be consumed from an artificially-flavored 500-ml beverage (lemonade flavour) at a quantity equivalent to the exercise-induced energy expenditure (aerobic metabolism) determined from a regression equation of oxygen consumption to bike power output established during the VO2max test on Visit 2. The control (no sugar) condition will comprise a taste-matched non-caloric placebo beverage, with the exercise calories added as fat to the evening meal (see LCHF). After exercise and drink ingestion, participants will shower (if desired) and rest seated in the laboratory prior to consuming a low-carbohydrate high-fat (LCHF) dinner meal at 19:00h (or + 2 h post exercise). Participants will then leave the laboratory, under instructions to abstain from consuming any food or drink other than water for the rest of the evening. Visit 5. On Day 2 of the metabolic trial, the participants will report to the lab at 06:30h. The CGM will be recalibrated. A venous catheter will be placed into an antecubital vein by a trained person (David Rowlands, Claire Badenhorst, or certified person) for fasting and postprandial blood collection. A high glucose drink containing 75g will be ingested at 07:00h for assessment of Oral Glucose Tolerance response. Blood samples will be collected at time=0, 30, 60, 120 min. The catheter will be maintained patent with saline flush and removed after the 120 min sample. Participants will have consented to the blood collection and have the option to have remaining blood sample returned if requested. The remaining meals will be mixed macronutrient meals following the same macronutrient split as day 1. The standardized meals at the given times; 10:00hr, 13:00hr and 18:00hr. Some of the study meals will contain animal products (meat, dairy) are not suitable if for participants following a vegetarian or vegan diet. Blood glucose will be monitored via GCM to the end of Day 2 with special note to post-prandial responses to all meals throughout Day 2. Visit 6. On an agreed day following Visit 5, the researchers will collect or participants will return the transmitter devices to the lab for cleaning and reuse. Protocols. Exercise tests will be conducted using the electronically braked cycle ergometers (VeloTron, Racer Mate, Seattle, WA) and gas analysis using a calibrated Moxus MaxII Metabolic System (AEI Technologies, Naperville, IL). Exercise Protocol. A 5 minute warm-up at 50 W will be completed before the participants complete 10x1-min sprint intervals at ~80% Wmax spaced between 1-min recovery intervals which will involve slow riding at 50W. The exercise will finished with a 5 minute cool down at 50 W. The rating of perceived exertion (RPE) will be recorded after each 1 minute interval using the Borg Scale of RPE. Carbohydrate drinks. The drinks will comprise lactose or sucrose (Brewshop, Countdown) added to half-diluted (water) artificially-sweetened and flavoured diet drink. The placebo will be the artificially-sweetened and flavoured diet drink without any sugars added. The energy of the carbohydrate beverages will match the exercise-induced energy expenditure measured from the VO2-power regression established during the VO2max test. Standardised Diet. Each participant will receive the same food, the quantity will be relative to resting energy expenditure (REE). To individualise diets to each participant, daily energy intake is calculated by the Cunningham equation will be used, with energy from basal physical activity accounted for with 1.4*RRE. On day 1, 90% of daily energy was provided at main meals: 30% at each breakfast, lunch, and dinner and 10% of daily energy was a mid-afternoon snack. The macronutrient composition of the breakfast, lunch and snack meals will be followed; ~55% carbohydrate, ~30% fat and ~15% protein. All meals provided will be pre-packaged (e.g., yoghurt, muesli bars, pre-made meals etc) items purchased from local supermarkets. The day 1 dinner will be consumed at plus 2 h after exercise (e.g., 19:00h) in the lab and is LCHF dinner, which consists of tuna, steamed veges, butter, almonds (~5/80/15% carbohydrate/fat/protein). All subsequent meals will be consumed under free-living conditions and will be pre-packaged mixed-macronutrient meals following the same macronutrient slit as day 1. Breakfast at 7:00h, which will be a high glucose meal consisting of 75g of glucose in water. Participants will be asked to record the actual exact start time and food they ate/drank under free living conditions through diet recall sheets provided. Water and other non-caloric beverages will be allowed within a prescribed maximum quantity of caffeinated beverages of 3 per test day. Continuous Glucose Monitoring. To measure blood glucose levels, CGM will be used throughout each of the 2-day trials. GCM is a tool to identify glycaemic response to food and exercise outside of the laboratory setting. The sensors (Medtronics Guardian Connect) record interstitial blood glucose concentration and will be inserted into the upper arm about 12 h prior to the first meal of the trial to be consumed on Day 1. Blood glucose information recorded on the sensor will be read through a transmitter and recorded through the specific software downloaded on participant’s iphone/ipad/Android device; if a participant does not have a compatible device, the researchers will provide an ipad. Catheter inserted for calibration of CGM