This human study will be a pilot trial that will precede a planned more long-term intervention trial. It will focus on young adults (age 18 to 25 y). The main purpose is to study whether the healthy lifestyle recommender solution, reflecting a multi-portfolio intervention and developed within this project, is well accepted by the participants, has a decent adherence (i.e. user time of the app), and whether the overall design is well suited to the participants, in order that they will improve dietary habits. This study will be of longitudinal design without a control group.

At present, numbers of persons with overweight and obesity continue to grow in most countries worldwide. Young adults are at risk since in in this period of life most people start to be independent from their families, with the consequent decisions about their food and lifestyle choices. It is frequent that at this time an increase in irregularity of meals and unhealthy food choices, occurs, together with changes in physical activity habits and social or individual pressures. Because of this, it is essential to give tools to these individuals that will allow them to make healthy choices and to have healthy habits, since they will be the future adult population that will raise and inspire the next generation. As solutions to combat the trend toward increasing overweight and obesity are much in need, the present study aims to intervene with the developed healthy lifestyle recommender solution to address various factors known to constitute a risk for developing obesity, including socio-demographic aspects, psychological/behavioural ones, physical activity, dietary patterns, among other. Such a multi-dimensional portfolio approach is believed to be very much needed for the prevention of obesity and co-morbidities, and the personalization of the solution, as well as the nudging/gamification.

The applied intervention with the developed healthy lifestyle recommender system will be unique and is not used in any other clinical study. However, a large number of intervention studies on young adults' obesity, considering nudging (e.g. 60 in www.clinical.trials.gov), were found. Among the registered clinical trials in the referred database, 3 considered young adults obesity and saliva salivary analysis.

The investigators judge the risk for the participant as low, since only saliva will be collected which collection is totally non-invasive. The administered intervention is expected to be effective, based on the multi-level nature of the tools applied.

This is a longitudinal study, non-controlled. Participants will receive the developed healthy life-style recommender solution for the duration of the study, and endpoints within subjects will be compared before and after.

The investigators are aware of the potential influence of seasons and other longitudinal changes on the outcomes, however as the endpoints are rather motivation and adherence, the investigators deem the design as appropriate. Moreover, in case of salivary parameters, which can be more sensitive to this type of variation, the collection in three successive days, before and at the end of the trial (to be analysed as pooled samples) will minimize these potential effects.

The intervention is the developed eHealth solution, i.e. the healthy lifestyle recommender system. It is based on a previously developed meal recommender system, but will be much extended, resulting in a multilevel portfolio intervention regarding:

1. Suggesting personalized meal recommendations,
2. Proposing physical activities tailored to the individuals' capabilities and preferences,
3. Measuring and considering emotional and psychological parameters,
4. Proposing additional healthy life-style patterns regarding e.g. sleeping patterns, alcohol and tobacco consumption, engaging in social activities etc.

The detailed nature of the interventions will first be developed during co-creation and then targeted to the participating individual. The intervention will include collecting urinary and saliva samples, as well as measuring anthropometrics and collecting data (personal, socio-demographics, general health and well-being, physical activity and eating patterns, among other) via questionnaires.

The study duration will be 3 months from the official start to the end. Following a first interview to test participants eligibility, the investigators have compiled a list of exemplary endpoints in the following, providing an overview about the sampling frequency.

Young adults (age 18-25 y) will be recruited via university and local hospital (Hospital do Espirito Santo - Évora), with help from the researchers from the School of Health Sciences, by direct advertisement and by recommendation of Hospital dietitians. The run-in time of the study will be long enough to assure recruitment of the required number of persons. The participants will be followed up regularly by phone-calls from the team of the University of Évora (e.g. weekly), and via contact maintained through the developed healthy lifestyle recommender solution. Should recruitment be insufficient, additional advertisement via local newspapers will be carried out, and the run-in time be extended.

Participants will receive the developed healthy lifestyle recommender solution. The individuals will then make use of the healthy lifestyle recommender solution for the entire study, i.e. a personalized, multi-level portfolio intervention will be tailored to the individual. The details of this intervention, including also nudges and gamification aspects will have to be developed during the project (WPs 2). Weekly phone-calls with participants from both groups will assure further adherence to the study.

Collected samples (month 0 and month 3) will be stored locally at University of Evora. All data and questionnaires will be collected by trained personnel, using RedCap platform. Data will be stored under a protected server, under the responsibility of Luxemburg Institute of Health, which is the leading institution of the project HealthyW8, under which this study is being developed. Individual data will be not linked to participants identification, since each participant will receive a code, at the beginning, answering all questionnaires and collecting all the samples under that identification (code). Only the researcher responsible for the study will have assess to the correspondence between identification and codes. This correspondence will be stored in an external drive, safely stored in the University of Evora and without being connected to internet.

The intervention will only require the healthy lifestyle recommender solution in form of an app. In addition, participants in the intervention arm will be able to access the Open Stakeholders Platform to access further information on healthy living. All data collected will be compiled in clinical report forms that will be generated by the University of Evora team. Saliva will be collected by trained researchers from the University of Evora. Regarding questionnaires, the investigators will use previous developed and validated questionnaires, such as the IPAQ questionnaire for physical activity or the SF-36 questionnaire for healthy lifestyle.

Inclusion criteria:

• To be young adult (age 18-25 y)
• To reside in Portugal
• To be overweight (BMI between 25-30 kg/m2)
• Women and men

Exclusion Criteria:

• To have a manifest chronic diseases (e.g. cancer)
• To be already in energy restriction or following a specific diet (on their own or advised by their physician)
• To have eating behavior pathologies.

The investigators will follow the General Data Protection Regulation (EU) 2016/679 of 27 April 2016 (known as the GDPR) and all subsequent texts replacing or supplementing this Regulation Before the start of the study, all subjects will be informed about the aim of the study, the study protocol, as well as risks/benefits.

Only the researcher responsible for the study will have access to the correspondence between identification and the codes generated. This correspondence will be stored in a computer protected with password, not linked to internet and in a drive, stored in the University of Evora. All data (questionnaires, samples, etc.) will be identified with the participant code and not personal identification. Data will be presented treated, and no individual data, that could allow participant identification, will be public presented.

From the beginning until the final of HealthyW8 project (from 2025-2028)

Only the researcher responsible for the study will have access to the correspondence between identification and codification. All the other researchers will have access only to codified individual data. Individual data will be shared only with the researchers responsible for statistical analysis and not public presented.