The influence of gene variants on physiological responses to a Mediterranean diet - a nutritional genomics focus,

Clinical Sessions (approximately 3 hours each): Eligible participants will be asked to attend the Clinical Trial Suites at RMIT University Bundoora (Building 203) and asked to bring the signed consent form. Participants will be asked to complete a personal information and medical questionnaire. During the initial (baseline) clinical session participants will perform a standard buccal swab (this will not be repeated in subsequent clinical sessions). Each buccal swab will be used for genetic profiling using Single Nucleotide Polymorphism arrays. During the clinical session participants will be weighed, measured for height and have their hip to weight ratio recorded. Blood pressure will be measured using a sphygmomanometer. Participants will have their body composition measured using Dual-Energy X-ray Absorptiometry (DEXA). Participants will then be asked to wear a respiratory mouth piece and nose clip (for approximately 10 mins) to have their respiratory gases measured every 30 seconds via an open-circuit sampling system. Respiratory data will be used to determine resting metabolic rate and each participant’s daily energy requirements. Following this, participants will perform a standard oral glucose tolerance test (OGTT) to determine glucose handling. Blood samples will be taken prior to, at 30-mins, 60-mins and 120-mins following glucose ingestion for subsequent measure. Habitual dietary intake will be measured using a 3-day food record (2 weekdays and 1 weekend day). Participants will be asked to complete a food frequency questionnaire. Dietary quality will be assessed using the Healthy Eating Index (Basiotis et al. 2002). Mood State will be analysed using the Profile of Mood State questionnaire and the Hospital Anxiety and Depression Scale questionnaire. These questionnaires will be administered whilst the participants are undertaking the OGTT. Stool samples will be collected by participants using a stool collection kit. During the 1st and 2nd clinical session, the participant will also consult with the Accredited Practising Dietitian for approximately 45min-1hour to explain the dietary intervention phase and to collect food diaries. In the final clinical session the Accredited Practising Dietitian will also meet with the participant to collect final food diaries and food frequency questionnaires. Following the initial (baseline) clinical session participants will be eligible to commence the dietary intervention and will be randomly assigned to either the 8-week Mediterranean dietary intervention or the 8-week General Healthy Eating intervention (Control). This dietary intervention timeframe has demonstrated physiological changes on a molecular and metabolic level (Bondia-Pons et al. 2015; Marques-Rocha 2016). This study will be analysed as a parallel design. Dietary Intervention Mediterranean (8-weeks): Each participant will receive a detailed sample Mediterranean meal plan, recipes, and education material to assist with adherence to a Mediterranean diet for the 8-week period. This will be explained by an Accredited Practising Dietitian during the clinical session. This task will be facilitated by providing a calibrated scale, a menu plan to each participant, along with a food hamper with food items that will be used as part of a Mediterranean diet. Each Mediterranean meal plan will adhere to the Mediterranean diet developed in the Mediterranean Diet Model in Australia: Strategies for Translating the Traditional Mediterranean Diet into a Multicultural Setting study (George et al. 2018) and the validated protocols used in the PREDIMED trials (Martinez-Gonzalez et al. 2012). This includes using extra virgin olive oil (minimum 3-4 tablespoons per day), eating vegetables with every meal (100g leafy greens, 100g other vegetables, 100g tomatoes per day), at least two serves of fruit per day, legumes at least twice per week, at least three serves of fish per week, red meat less often, one serve of nuts daily, two serves of dairy daily (milk and yoghurt preferable), cheese in moderation (three days per week preferably feta, 1 serve equalling 30 grams), choice of wholegrain breads and cereals, consuming 3 eggs per week, sweets to be consumed in moderation (preferably homemade), red wine is optional (0-2 standard glasses per day, with meals, instructions to not get intoxicated). Advice on alcohol will be provided to those who already consume alcohol in their habitual diet. Dietary Intervention General Healthy Eating (8-weeks): Each participant will be provided with general healthy eating advice in accordance to the Australian Guide to Healthy Eating (AGTHE). This task will be facilitated by providing the participant with relevant education material, a guide to food groups and portion/serve sizes, with a focus on high fibre, low fat eating and reduced intake of discretionary foods. This diet has been chosen as a control diet based on previous literature and to also reflect current dietetic advice provided in practice to the Australian population (Papamiltiadous et al. 2016; Itsiopoulos et al. 2018). Dietary intake will be measured using a 3-day weighed food record during the intervention mid-point (week 4) and the week before the end of each dietary intervention (week 7/prior to the post intervention clinical session). Adherence to the Mediterranean diet will be assessed using the Mediterranean Diet Adherence Screener Score (MEDAs) tool. An ad libitum approach for each diet will be advised, based on previous literature (Papamiltiadous et al. 2016; Jacka et al. 2017; Itsiopoulos et al. 2011; Itsiopoulos et al. 2018; Ryan et al. 2013). The participant will consult with the Accredited Practising Dietitian during the clinical sessions for approximately 45-60 minutes. The participant will also receive weekly telephone calls to support the participant throughout the dietary intervention. Participants will be instructed to maintain their habitual physical activity patterns during the intervention, with physical activity patterns monitored and evaluated weekly by informal individual support-orientated phone calls throughout the 8-week intervention. Food recall strategies will be adopted by researchers throughout these phone calls to monitor and evaluate dietary compliance.