Effects of a low carbohydrate diet on heart failure symptoms and quality of life in patients with diabetic cardiomyopathy.

The intervention group (low carbohydrate diet): For the purpose of this study, participants will be coached by the student researcher who will be guided by a qualified dietitian, to follow a LC diet as defined by an intake of less than 130g of carbohydrate per day (Hite et al., 2019). To achieve a CHO ingestion of less than 130g per day, the participants will be instructed to enjoy a variety of above ground and green, leafy vegetables. Small amounts of fruit, starchy vegetables such as potatoes, sweet potatoes, parsnip, peas and corn, nuts/seeds and legumes are permitted. Participants are encouraged to eat freely from animal and plant proteins such as chicken, fish, unsweetened dairy products and tofu. Participants will be coached to avoid high CHO foods such as bread, rice, pasta, sweetened beverages and alcohol. Food lists using a “traffic light system” will be provided to the participants as a reference and to enhance compliance with the diet. These lists categorise foods and drinks into: Always/every day (green list), sometimes (orange list) and avoid (red list). Minimum Dietary protein intake level will be set to 1.2 – 1.7 g/kg of ideal body weight, in keeping with both the Clinical Guidelines for Therapeutic Carbohydrate Restriction (Hite et al., 2019) and the Australian Dietary Guidelines (National Health and Medical Research Council, 2013). Dietary fat intake will not be restricted. Dietary sodium intake will be limited to <2g/day in accordance with The National Heart Foundation of Australia and Cardiac Society of Australia and New Zealand guidelines for the prevention, detection, and management of HF in Australia (Atherton et al., 2018). A 16-week time frame for the intervention has been proposed. In the first month the participants will be introduced to the low carbohydrate diet. Participants will be invited to attend a 60-minute group counselling session, once per week in the first 4 weeks and fortnightly individual 60-minute sessions for the following 12 weeks. Sessions will be held face to face, via phone call or via video conferencing if the participants prefer. Participants will be requested to change their diet gradually over the initial four weeks and should ideally have adjusted all their meals to the low carbohydrate recommendations when attending the fourth session at the end of the first month. The counselling sessions will focus on discussion of the underlying mechanisms that drive type 2 diabetes and heart failure, instructions on dietary carbohydrate restriction, food selection and meal preparation, interpretation of food labels, recognition of potential side effects, establishing mindful eating techniques, difficulties in adhering to the diet and support for health behaviour change. Dietary counselling will be adapted to the personal, as well as the religious and cultural food preferences of the participants. All study participants will be offered the opportunity to invite a member of their family/household to attend the education sessions if they chose. Participants will be asked to complete three 24-hour dietary recalls using the validated INTAKE-24 AUS computerised dietary recall system (Simpson et al., 2017). The recall diary will specifically monitor the food intake of two weekdays and one weekend day at baseline, week six and at the end of the intervention (week 16). This way, the extent of the patient’s dietary changes will become apparent. INTAKE-24 AUS is based on the original web-based system INTAKE-24 UK, developed by researchers at the Human Nutrition Research Centre at Newcastle University (Simpson et al., 2017). INTAKE-24 AUS provides a reliable, affordable and user friendly 24-hour dietary recall system (Simpson et al., 2017). Based on the multiple-pass 24-hour recall (Raper et al., 2004), INTAKE-24 AUS includes an extensive variety of foods commonly eaten in Australia, linked to nutrient composition codes (Foster et al., 2019). As the user is prompted through the recall process, the inclusion of food images enables easy portion size estimation by participants without the need for weighing of food (Simpson et al., 2017). The advantage of this web-based recall system compared to other methods is that it enables the participant to complete the recall where and when it is convenient for them. In addition to this, participants will be invited to complete a mini food frequency questionnaire (FFQ). The food questionnaire is a self-administered assessment tool to estimate food frequency intake over a specific period of time. Dietary counselling will be adapted to the personal, as well as the religious and cultural food preferences of the participants.