Study design and experimental protocol
fasting venous blood sample
Participants completed two, 1-day laboratory-based trials in random order: a high GI trial and a low GI trial. The lead investigator enrolled the participants in the research and randomly assigned the participants to each experiment in a counterbalanced manner using computer-generated random numbers. The interval between trials was at least 7 d. All trials were conducted during the follicular phase of the menstrual cycle (days 1–10), based on the self-reported onset of menstruation. A schematic illustration of the study protocol is shown in Schematic illustration of the study protocol. GI, glycaemic index; VOIn both trials, all participants reported to the laboratory at 08.30 after a 10-h overnight fast (no food or drink, except water). Body mass was measured to the nearest 0⋅1 kg using a digital scale (MC-780A-N, Tanita Corporation, Tokyo, Japan). A heart rate monitor (Polar RCX3, Polar Electro, Kempele, Finland) was then fitted to measure heart rate continuously throughout the trial. After a 10-min seated rest, subjective appetite using a paper-based questionnaire (details in ‘Subjective appetite’), food reward using the LFPQ-J (details in ‘Food reward’), and baseline measurements of a 15-min resting expired gas sample were obtained sequentially. Thereafter, a cannula was inserted into the arm vein, and a fasting venous blood sample was collected in a seated position. The participants then consumed a high or low GI meal at 09.00. Participants were asked to consume the test meal over 20 min (i.e. the last bite was set at 09.20), and the order of food intake in each meal was standardised. Subsequently, they were required to rest for 100 min before performing the exercise. During the 60-min walking exercise on the treadmill at a speed eliciting 50 % of the estimated maximum oxygen uptake (determined from the preliminary test) (11.00–12.00), oxygen uptake, respiratory exchange ratio (RER), fat oxidation rate, and carbohydrate oxidation rate were measured using a stationary gas analyser (Quark RMR, COSMED Co. Ltd., Roma, Italy), and RPEs were assessed periodically.