The effect of a high protein low carbohydrate meal compared with a control meal on morning and evening glucose responses in healthy adults.

BRIEF NAME High protein low carbohydrate (HP/LC) test meal. WHY Postprandial glucose responses are elevated in the evening compared with the morning. This may be a risk factor for Type 2 diabetes for those who frequently eat at night, e.g shift workers. The purpose of this study is to determine if a high protein low carbohydrate meal is an effective strategy for lowering evening glucose responses compared with a control meal. WHAT Materials: All participants will be provided with a standardised test meal to consume (vegetarian pasta with sauce and a milkshake) at the study session, which is pre-prepared by the researchers. The total energy content for the HP/LC test meal per serve is 3.26MJ, with 41% of energy from protein, 28% from fat, and 29% from carbohydrates. During the intervention a paper based 100mm Visual Analogue Scale will also be administered to participants asking them to rate their hunger and fullness. All participants are provided with a standardised pre-study session meal which is to be consumed at least 10 hours prior to attendance at the research facility, i.e. last meal before commencing 10 hour fast. This pre-study session meal consists of the following store bought items; vegetarian frozen meal, low fat yoghurt, and packet of nuts. Materials used to collect anthropometric measurements include; scales, stadiometer, Medical Body Composition analyser SECA, and automated blood pressure monitor. The researchers will use an automated clinical chemical analyser to measure the plasma glucose concentrations of blood samples. The plasma insulin concentrations will be analysed using a human insulin ELISA kit and measured on a microplate reader. Procedures: Upon arriving at the research facility, after a 10 hour fast, participants will have their anthropometric measurements taken including weight, height, body composition and blood pressure. A trained phlebotomist will fit an intravenous cannula in the arm and one baseline blood sample will be taken at time 0 minutes. Participants will then be given the test meal (either the HP/LC or an isocaloric control) to consume within 15 minutes at either 8:00am in the morning session or 8:00pm in the evening session. Blood samples will be collected at subsequent time points: 15, 30, 45, 60, 90, 120 and 180 mins after participants commenced eating the meal. At each time point participants will also be asked to mark a 100mm Visual Analogue Scale rating their hunger and fullness. WHO PROVIDED The cannulation of participants and blood collection will be carried out by a trained phlebotomist or nurse who has experience with cannulation. HOW The study sessions will be carried out face to face, in groups of no more than 3 participants. WHERE The study sessions will be carried out in the Be Active Sleep and Eat (BASE) Facility laboratory located in Notting Hill, Victoria. WHEN and HOW MUCH Each participant will attend 4 study sessions in total (2 testing the HP/LC meal and 2 testing a control meal), each session will run for approximately 3.5 hours. Study sessions are scheduled based on convenience and there will be a minimum wash out period of at least 7 days between sessions. The ordering of sessions will be determined based on the availablility of the phlebotomist and the participants’ schedule.