Inadequate plant food intake is a leading modifiable risk factor for non-communicable disease. However, on average, 88% of individuals do not consume adequate amounts of vegetables. Using digital technology may help improve health behaviours , with this potentially providing an accessible route to increasing plant food intake. However, uptake and engagement with applications designed to influence health behaviours is generally poor , and few studies have examined the main factors supporting user engagement and retention. Personalised dietary feedback, such as the provision of personalised advice or recipes, has the potential to enhance this process. However, whether nutritional interventions utilising personalised dietary feedback support user interaction, engagement, and retention remains to be studied.

Hence, the proposed project is a proof-of-concept study aiming to assess the effectiveness of using an application with personalised dietary feedback to support increased healthy plant food intake. 315 healthy males and females, between the ages of 18- and 45-years who self-report less than 50% of the recommended intake of vegetable consumption will participate in the study.

Before the intervention, participants will receive web-based instruction on the use of the smartphone application. Subsequently, participants will log all meals for two-weeks using the application to generate a baseline plant food consumption profile. In the baseline period, participants will wear a continuous glucose monitor. This will inform their individualised goals and possible feedback for the intervention period. The intervention will be 4-weeks in duration, consisting of the use of a personalised dietary program application, which will provide both recipes and feedback. Those randomised to the control will only have access to the meal logging feature. Throughout this period, participants will wear a smartwatch to track sleep metrics such as sleep onset and duration. Following the four-week intervention period, participants will be able to continue using the app for a six-week period, during which engagement with the application over time will be ascertained via telemetry. At the end of the follow-up, participants will receive an exit questionnaire to provide insight on their experience with the application, attitudes, habits and knowledge regarding consumption of plant foods, and self-perceived impact on health and dietary habits.

To provide mechanistic insight, a subset of participants (n = 50) will visit the laboratory at the University of Bath on two occasions (approximately 45 minutes each) - baseline and post-intervention. During laboratory visits, participants will provide blood pressure and body weight measurements, as well as saliva and venous blood samples. Saliva samples will be assessed for salivary cortisol, and blood samples will be assessed for the following: plasma glucose & insulin; plasma uric acid; plasma ascorbic acid; plasma tocopherols; serum carotenoids; plasma cytokines; plasma CRP and ferritin; F2-Isoprostanes; immune cell inflammatory capacity; HbA1c.

Inclusion Criteria:

• Healthy males and females, age at start of the study ≥ 18 and ≤ 45 years;
• Non-rejectors of Knorr (due to the recipes in the PDP application);
• Currently cooking or intending to cook (*themselves or partner) at least one main meal at home for at least five days a week;
• Indicated desire to eat more vegetables;
• In possession of an Android or iOS-based smartphone;
• Willing to use an app to receive information and log all meals daily;
• Currently using or willing to use a smartwatch;
• Able to provide informed consent.

Exclusion Criteria:

• High reported baseline veg intake (participants need to self-report less than 50% of the UK rec / self-reported intake above the UK adult average (206 g/2.6 servings));
• Reported participation in another nutritional or biomedical trial within 1 month before the screening or during the study;
• Planned frequent travel (>2/month) and travel to countries with time zone >GMT +04:00 during the study period;
• Habitual consumption of >14 units (female participants) and >21 units (male participants) alcoholic drinks in a typical week;
• Reported start or change in use of any nicotine containing products directly preceding the study or during the study itself;
• If female, is pregnant (or has been pregnant during the last <3 months) or will be planning pregnancy during the study period;
• If female, is lactating or has been lactating in the 6 weeks before screening and/or during the study period;
• Reported dietary habits: medically prescribed diet, slimming diet, any condition or self-prescribed diet that restricts consumption of vegetables, not used to eating at least 3 meals a day;
• Reported body mass loss/gain (>5%) in the last 3 months before the study. Self-reported history of major depressive disorders and/or current use antidepressive/antianxiety medication;
• Clinically diagnosed sleep disorders and/or use prescribed sleep medication. Taking medication (including traditional medicines and or dietary supplements) which may pose undue personal risk or introduce bias into study measurements, as judged by the PI;
• An allergy to adhesives, which would prevent proper attachment of the CGM;
• Being an employee of any company developing personalised diet applications, including Salus Optima or Unilever.