The goal of this clinical trial is to help prevent the development of type 2 diabetes (T2D) in adults who are at risk. The study will test a digital intervention called VA|PREVENTION, a web application designed to support and promote healthy behaviour changes known has T2D risk factors, such as physical activity, diet, and sedentary behaviuor. The main questions this study will explore are:• Is the VA|PREVENTION web app, which includes a virtual human coach, effective in preventing type 2 diabetes?• Can the VA|PREVENTION web app be successfully implemented in real-world settings?• Is the VA|PREVENTION web app cost-effective?• Is it safe for participants to use?To answer these questions, the study team will compare the VA|PREVENTION web app to an openly available guidebook that provides standard information about preventing type 2 diabetes.Participants will complete the following activities:

• Participants will be randomly assigned to one of two groups: one group will use the VA|PREVENTION app, while the other group will have access to an openly accessible guidebook on T2D prevention.
• Participants will be in the study for 10 months.
• Participants will be assessed at the start of the study (baseline), and again at 4 months and 10 months.
• Assessments will include body measurements (such as weight, height, and waist circumference), physical activity levels, and responses to questionnaires.

T2D risk adults will be invited by nurses and community pharmacists, leveraging their trusted roles within the healthcare system. Recruitment activities will prioritize fair treatment and respect for informed consent. Only participants fully capable of understanding the informed consent terms will be included in the study. Potential participants will receive detailed information about the study's purpose, procedures, potential risks, and benefits. After providing time for questions and discussion, written informed consent will be obtained. Following consent, participants will undergo screening to confirm eligibility according to predefined inclusion and exclusion criteria. Those meeting all eligibility criteria will proceed to the baseline visit (T0), during which initial assessments will be conducted. After the baseline assessment, participants will be randomized into one of the study groups. Following randomization, the assigned intervention will be initiated, with subsequent visits scheduled at 4 months (T1) and 10 months (T2) for data collection.Upon obtaining informed consent, participants will undergo screening to verify eligibility according to predefined inclusion and exclusion criteria. Those who meet all criteria will proceed to the baseline visit (T0), where initial assessments will be conducted. Following this, participants will be randomly assigned to one of the study groups. The assigned intervention will then be initiated, with subsequent visits scheduled at 4 months (T1) and 10 months (T2) for data collection. At these timepoints, waist circumference, the primary endpoint, as well as data on anthropometric measurements (heigh and weight), diabetes risk (FINDRISC score), dietary adherence (through MEDAS questionnaire), physical activity (through accelerometry measurements), and health resources utilization will be collected.

Inclusion Criteria:

• Age ≥ 18 years old;

• FINDRISC Score ≥12 (moderate, high or very high) and/or prediabetes, defined as either:

  • HbA1c between 5.7%-6.4% within the last two years; or
  • Impaired Glucose Tolerance (IGT) based on an Oral Glucose Tolerance Test (OGTT) at the 120-minute mark, with values between 140 and 199 mg/dL in the past three years;

• Able to understand, speak and write Portuguese;

• Able to provide written informed consent;

• Access to a smartphone, tablet or computer with internet connection;

• Plan to reside in the recruitment/study area for the next 10 months

Exclusion Criteria:

• Established Type 1 and 2 Diabetes Mellitus diagnosis;
• Pregnancy - Self-reported as currently pregnant, planning to become pregnant, or not practicing contraception, in the following 10 months (if applicable);
• Conditions precluding technology use (e.g. cognitive decline, dependent upon a carer for daily activities);
• Use of anti-obesity or diabetes medication, such as Metformin, Glucagon-like peptide-1 analogue (GLP-1), or other medications known to significantly impact weight (either gain or loss), currently or within the preceding 3 months;
• Following a prescribed medical diet;
• Having undergone bariatric surgery within the past 3 years or planning surgery within the next 10 months;
• Any mental health condition, including, but not limited to, eating disorders or alcohol/substance abuse, that would impact fully participating on the study;
• Participating in a concurrent weight management program and/or relevant interventional research protocol;
• Contraindication to physical activity or weight loss;
• Existing thyroid disorder;
• Active cancer or less than 6 months from treatment;
• Unable to provide informed consent or absence of a legal representative that can provided it on behalf of the patient;
• Institutionalised adults;
• Foreseeable difficulty in attending study visits.

The data will be made available in an aggregated form and will not be directly linked to the participants, making it impossible to associate the data with their identity. This data will be accessible on the national open-access repository promoted by the project's funder Fundação para a Ciência e Tecnologia (FCT), known as the Polen repository. Access will public for studies previously submitted and approved by an ethics committee and are deemed relevant, allowing other researchers to use it to advance scientific research and the development of new solutions in the healthcare field.

Data generated by the study will be made publicly accessible within 18 to 24 months following the completion of the project studies.

Access will be granted through the Polen repository, which is provided by Portugal's national science funding agency, Fundação para a Ciência e a Tecnologia, I.P. (FCT).