The Effects of Exercise on Glycaemic Response of Low or High Glycaemic Index Meals
Condition: Glycaemic Response
Study type: Interventional

Summary: 
      The aim of the current study is to determine the effect of sprint interval training (SIT) in
      conjunction with either high or low glycaemic index meals (breakfast, lunch and dinner) on
      the 24-hour glycaemic profile and glucoregulatory hormones in Asian males.
    

Detailed description: 
      The study will recruit 20 young healthy Asian men of Chinese descent. Subjects will visit our
      Clinical Nutrition Research Centre (CNRC) on 5 occasions: once for consenting, screening and
      familiarization with the exercise and testing equipment (screening), and four additional
      times, interspaced by a minimum of 3 days, to undergo a total of four study conditions. The
      four study trials combine SIT or rest and low or high GI diet in a 2 x 2 design, and will be
      assigned in randomized order: (RL) Rest and low GI, (SL) SIT and low GI, (RH) Rest and high
      GI, and (SH) SIT and high GI. The test conditions will have comparable foods with RL and SL
      diets comprising local foods of low glycaemic index and RH and SH diets comprising local
      foods of high glycaemic index. Randomization of study trials will be carried out using an
      online randomizer (www.randomizer.org/). In the SL and SH trials, subjects will perform a SIT
      bout consisting of alternating periods of low-resistance cycling (4 ½ minutes) and maximal
      effort all out cycling (30 sec Wingate test) for a total of 30 min (i.e. a total of 6 Wingate
      tests)*, whereas in the RL and RH trials, subjects will rest for the equivalent period of
      time (i.e. 30 min). For screening, potential subjects will come in the morning after an
      overnight fast. After obtaining informed consent, a series of screening tests will be
      conducted, including questionnaires (general health, physical activity and eating behaviour),
      anthropometry (height, weight, waist and hip circumference), blood pressure, resting heart
      rate, fasting blood glucose, HbA1c and body composition by air displacement plethysmography
      (BodPod, Cosmed, Rome, Italy). Following enrolment, subjects will undergo assessment of
      resting metabolic rate (RMR) for 30 minutes using a ventilated hood system (Quark CPET,
      Cosmed, Rome, Italy). RMR will be multiplied by a factor of 1.5 to approximate total energy
      requirement for weight maintenance. This will allow for tailoring the caloric content of the
      test meals to each subject's energy requirements. Thereafter, subjects will eat a small
      standardized breakfast and they will perform a 30-min SIT session to get familiarized with
      the exercise and the equipment. The total time required for screening will be around 2 hours.
      After the screening, subjects will be provided with a food diary to record all food intake on
      Day 1 and an activity diary to record all activities on Days 1 and 2 of the actual study
      trials (see below). Although only sedentary subjects will be recruited (=60 min of
      moderate-intensity exercise weekly), they will also be instructed to refrain from any
      vigorous activities during the three days before each study trials and throughout its
      duration. On Visits 2 to 5 (four experimental trials, in random order): Each of the four
      study visits will last for approximately 12 hours (spanning over 3 days), during which the
      following will take place: On Day 1, subjects will come to the Lab at around 4:00 pm to have
      the continuous glucose monitoring system (CGMS) inserted. CGMS will be used to measure 24
      hour blood glucose concentrations. The sensor records interstitial blood glucose
      concentrations every five minutes. This will involve the insertion of a small sensor under
      the skin in the abdomen, which will be carried out by using a device that produces minimal
      pain and discomfort. After insertion, the stabilizing and calibration procedures will take 2
      hours after which the subjects will go home with a standardized dinner to eat at around
      7:00pm. Subjects will have to refrain from eating after 10:30pm and return to the CNRC the
      following morning (Day 2).On Day 2, subjects will report to the lab at 8:15 am following an
      overnight fast for the first of the four study conditions. Upon arrival, an indwelling
      catheter will be inserted into the antecubital fossa or forearm vein of one arm and will be
      kept patent. Blood samples will be obtained after the insertion of the catheter at 8:30 am
      (time = -30 min). Between 8:30 am and 9:00 am, subjects will either rest for 30 minutes or
      perform the SIT bout which will start with 4 ½ minutes of low-resistance cycling followed by
      30 seconds of maximum effort, repeated for a total of 6 times*. During the SIT, subjects'
      ratings of perceived exertion (RPE) will be measured periodically using the Borg scale. At
      9:00 am, blood samples will be collected (time = 0 min), after which breakfast (low or high
      GI) will be provided. After finishing breakfast, at 9:15 am, blood samples will be collected
      every 10 minutes for the first half hour and every 30 minutes for the remaining 3 hours at
      15, 25, 35, 45, 75, 105, 135, 165, and 195 minutes. Before lunch is served at 12:45pm (time =
      225 min), blood will be collected and again after lunch at 1:00 pm (time = 240 min), followed
      by blood collection every 10 minutes for the first half hour and every 30 minutes for the
      remaining 3 hours at 250, 260, 270, 300, 330, 360, 390, 420 and 450 minutes. After the last
      blood sample is collected at 4:30 pm, the catheter will be removed and the subjects will be
      discharged from the Lab. Subjects will be provided with the last test meal of the day
      (dinner) to eat at home at around 7:00pm. Throughout the day and at specific times, subjects
      will complete computerized visual analogue scales (VAS) on hunger and fullness. Blood samples
      will be used to measure fasting and postprandial concentrations of glucose and major
      glucoregulatory hormones like insulin and glucagon. C-peptide concentrations will be used to
      provide estimates of insulin secretion with mathematical modelling. Blood lactate will be
      determined before and after exercise to verify maximal exercise effort. On Day 3, subjects
      will come to the Lab at 8:30 am for final calibration and removal of the CGMS sensor.
      Subjects will come to the Lab for visits 3, 4, and 5 to perform the other 3 experimental
      trials, with at least 3 days wash-out in-between visits.
    

Intervention name(s): High glycaemic index meal and exercise; High glycaemic index meal and rest; Low glycaemic index meal and exercise; Low glycaemic index meal and rest
Intervention type(s): Other; Other; Other; Other
Allocation: Randomized
Intervention model: Crossover Assignment
Intervention model description: Randomized cross over design
Masking: None (Open Label)
Primary purpose: Other