Preventing the Progression from Pre-Diabetes to Type 2 diabetes in New Zealanders Through Weight Loss: The PROGRESS NZ Study

The PROGRESS NZ Study is a prospective cohort study in individuals with pre-diabetes and early Type 2 diabetes, that has been designed to assess the relationship between body composition and glucose metabolism at baseline and in response to a dietary weight loss intervention. All individuals in the study will proceed to a weight loss intervention. Glucose metabolism at baseline and post the weight loss will be analysed using a hyperinsulinaemic euglycaemic clamp with stable isotope dilution and an arginine insulin secretion test. Body composition will be assessed using DXA scanning, whilst energy expenditure shall be calculated using hood calorimetry. Statistical analysis shall be with ANCOVA with assessment of the weight loss intervention; body composition (continuous variable) and their interaction. The weight loss intervention will involve undergoing an 'Optifast' very low calorie diet (VLCD) until 10% body weight is lost. This would be anticipated to take approximately 12 weeks to achieve if compliance is met. There is no maximum duration of diet determined. Optifast is a meal replacement supplement in the form of a shake. Individuals will be required to drink three Optifast shakes (meal replacements) per day as well as two cups of non-starchy vegetables and water. Each day of three shakes would provide 600calories per day, with 58g of protein and 39-71g of carbohydrate. An information sheet prepared by an Endocrinologist and dietician with experience in clinical research will be provided which shall detail the quantity of vegetables and type of vegetables permitted, as well as serving suggestions. Individuals will be contacted via telephone weekly to monitor progress and will visit the clinical facility (The University of Otago, Wellington Campus) monthly for a check-up including weight and blood pressure monitoring. Intervention adherence will be assessed using a combination of participant self-reported compliance and urinary ketone testing during the visits. In addition to the above interventional study, participants will then be invited to complete a six week exercise intervention, to assess the feasibility of the exercise protocol for larger research trials. This is not a compulsory component of the PROGRESS NZ study. This addition has full ethics approval. For those participants willing to take part, individuals will complete a six week exercise intervention one month after completing the Optifast diet. The intervention follows American College of Sports Medicine guidelines and will be fully supervised by an investigator trained in sports exercise and injury prevention. Participants will undergo a full cardiovascular examination, health questionnaire and 12 lead ECG prior to commencing exercise. The intervention will entail a six week programme, with 4 exercise sessions per week (40-60 min duration). The intervention will be a mixed high intensity interval training (HIIT) and resistance training (RT) programme. Prior to commencing the intervention, peak power (PP) for the HIIT (bike) intervention will be calculated. This will inform the power requirements for the first week of the protocol. Power requirements will increase by 2% per week thereafter. For the RT protocol, initial weight loading will be calculated based on the 'one rep max' (1RM). This will be increased by 1.5% each week. The programme will run as follows: Monday - aerobic HIIT . Five intervals (1,2,3,2,1 minutes) at 75% PP with 2 min rest periods at 30%PP Tuesday - RT. Seated leg press; chest press; hip thrusters; lat pulldowns; upright rows; overhead press - 3 x sets of 10-12 reps. Weights 55% of the 1RM. Thursday - speed HIIT - 10x 1 min intervals (905) PP with 2 min recovery intervals (30% PP) Friday - strength RT. Repeat of Tuesday. Prior to commencing, and after completion, participants will be invited to perform a full body DXA scan and oral glucose tolerance test. At the end of the intervention, participants will also be invited to complete a questionnaire assessing the feasibility, tolerability and cultural appropriateness of the intervention.