GlucoTRIG: measuring the impact of high carbohydrate and high fat composite meals on postprandial insulin and triglyceride responses in healthy adults – a randomised, controlled, crossover trial

The study is an acute, randomised, crossover design involving 15 healthy participants (male or female) and consisting of three treatment arms. All treatment arms will be isocaloric and only differing in macronutrient compositions. All participants will undergo all three treatment arms. The three treatment arms consist of (1) a reference meal of 480 kcal energy, 19.8g proteins (16.5%), 13.9g fats (26.1%), 66.1g carbohydrates (55.1%), and 3.1g fibre (0.6%); (2) a high-carbohydrate, low-fat test meal consisting of 479 kcal energy, 20g proteins (16.7%), 6.7g fats (12.6%), 81.3g carbohydrates (67.9%), and 4.1g fibre (0.9%); and (3) a low-carbohydrate, high-fat test meal consisting of 479 kcal energy, 22.9g proteins (19.1%), 27.1g fats (50.9%), 34.2g carbohydrates (28.6%), and 3.5g fibre (1.1%). Participants will be asked to complete a consent form for participation, a brief medical questionnaire, a health screening questionnaire, eating attitudes testing questionnaire, and a physical activity questionnaire at the screening visit. Screening visit will involve taking anthropometric measurements (weight, height, body muscle and fat mass, etc.), blood pressure, and a finger prick test to obtain fasting lipid profile and glycated haemoglobin A1c (HbA1c) for eligibility. Each study visit comprises 3.5 hours where eligible participants will arrive at the clinical facility at Massey University after an overnight fast (at least 12 hours). At each study visit, participants will be asked to provide a completed 24 h food recall record to ensure compliance and that there are no significant changes to their diet throughout the study. At each study visit, a venous blood sample (18 mL) for fasting glucose, insulin and triglycerides at time point 0 min (baseline) will be collected. They will then be given a meal to consume within 20 minutes. The meal ingestion will be timed and participants will have to finish their meal within 20 minutes. The plate will be visually checked to ensure there are no leftovers remaining. Following 3-hour post meal, another venous blood sample (18 mL) will be collected at 180 min for the same measurements. Blood draws will be taken by having the participant lie in a supine position and blood samples taken via venipuncture on the antecubital fossa region of the arm into blood vacutainers. Blood collected will be immediately centrifuged and aliquot for storage at -80degC until analysis. Primary measure includes measuring postprandial triglycerides and insulin levels after consuming reference and test meals on separate occasions. Postprandial glucose and inflammatory markers including c-reactive protein (CRP), interleukin-6 (IL-6) as a secondary measure will also be taken. The data will be used to calculate the GlucoTRIG value of each meal to rank the healthiness of each meal. There will be at least a week of washout between each visit. Participants will be instructed to maintain a consistent diet without any dietary alterations throughout the duration of the study. They are to also abstain from alcohol and beverages such as teas, coffees, and energy drinks (both caffeinated and decaffeinated), all health supplements, and strenuous activity during the 24h period before each study visit.