The SWIFT trial - Supporting weight loss in adults with whole-food diets, intermittent fasting and high-intensity interval training

Participants will be randomised to one of 5 intervention groups for a 12 month period followed by a further 12 month follow-up: 1) control, 2) brief support - will meet with researchers once a month for 5-10 minutes to be weighed and have a brief discussion about progress and to address any concerns, 3) self-weighing - will be asked to weigh themselves at the same time every day and enter weight into our online database, email feedback on progress will be provided once a month, 4) My Fitness Pal - participants will be shown how to use this online/mobile app which allows them to track their dietary intake. Participants will use the app daily for the first month and then one week per month for 11 months, 5) Hunger training - participants will be taught how to eat to hunger and satiety using a combination of fingerprick blood glucose testing and awareness of hunger types. Participants will meet face-to-face with a dietitian for a 2-hour training session on day 0, followed by a quick phone call to assess progress on day 2 and a 30-60 minute face-to-face session on day 14. Participants will be monitoring their blood glucose and using the booklet daily for the first fortnight, after which blood glucose monitoring becomes optional. They will continue to use the booklet daily for the second fortnight, and then one week every month for the remaining 11 months. While participants are randomised to a certain support group and thus have no choice in this, they are allowed to choose which diet and exercise regime they would like to follow over the course of the 24 month study (including group 1 - the control group). Potential dietary approaches they can choose from include the Mediterranean diet, a modified Paleo approach (allows limited legumes and dairy) and intermittent fasting (5:2 approach). The mediterranean diet approach encourages wholegrains, fresh fruit and vegetables but limits red meat, sugar and saturated fat. The modified paleo (whole-food diet) approach encourages consumption of minimally processed foods with an emphasis on plant foods and animal proteins, but limiting sugar or grain-based foods. Small amounts of dairy and legumes are permitted if wanted by participants. The intermittent fasting approach outlines restriction of energy intake on 2 days a week to a quarter of normal intake. All dietary interventions are given with an extensive printed resource with recipes and guidance, as well as a half hour session with one of the researchers to answer questions. Potential exercise approaches include current recommendations, or a home-based high-intensity interval training (HIIT) programme. Participants choosing current recommendations discuss their choice of exercise type with a researcher and HIIT participants undergo a medical assessment and a one-off HIIT session training with heart rate monitoring.