MELIORA Virtual Coach Intervention for Breast Cancer Prevention

Inclusion Criteria: MELIORA-HEALTHY study participants must meet all of the following criteria in order to be deemed eligible for study participation: * Reside in Greece, Lithuania, or Spain. * Be female and at least 18 years of age. * Have access to and be able to use a smartphone (iOS or Android) compatible with the MELIORA app. * Be willing and able to use the MELIORA app for the entire study duration. * Willing to provide informed consent to participate in the study. * Have at least one of the following behavioural or metabolic risk factors for BC, assessed in a random order (each site may determine the order that is most convenient for them) until eligibility is confirmed. If a risk factor is identified, the subsequent assessments can be skipped: * Increased alcohol consumption: More than 1 drink per day. * Increased body mass index (BMI): BMI ≥ 25 kg/m² or waist circumference ≥80 cm for normal weight individuals. * Physical inactivity: Not meeting World Health Organization (WHO) guidelines of at least 150 minutes of moderate-intensity or 75 minutes of high-intensity aerobic exercise per week during the last month. * Suboptimal diet: Low diet quality based on the rapid Prime Diet Quality Score Screener (rPDQS). MELIORA-PATIENTS study participants must meet all of the following criteria in order to be deemed eligible for study participation: * Reside in Spain or Lithuania. * Be female and at least 18 years old. * Have access to and be able to use a smartphone (iOS or Android) compatible with the MELIORA app. * Be willing and able to use the MELIORA app for the entire study duration. * Willing to provide informed consent to participate in the study. * Have been diagnosed with breast cancer (BC) within the last 6 months and/or currently undergoing treatment (chemotherapy, radiotherapy, immunotherapy, hormone therapy) and/or in active follow-up. * Have at least one of the following behavioural or metabolic risk factors for BC, assessed in a random order (each site may determine the order that is most convenient for them) until eligibility is confirmed. If a risk factor is identified, the subsequent assessments can be skipped: * Increased alcohol consumption: More than 1 drink per day. * Increased body mass index (BMI): BMI ≥ 25 kg/m² or waist circumference ≥80 cm for normal weight individuals. * Physical inactivity: Not meeting World Health Organization (WHO) guidelines of at least 150 minutes of moderate-intensity or 75 minutes of high-intensity aerobic exercise per week during the last month. * Suboptimal diet: Low diet quality based on the rapid Prime Diet Quality Score Screener (rPDQS). MELIORA-SURVIVORS study participants must meet all of the following criteria in order to be deemed eligible for study participation: * Reside in Spain, Lithuania, or Sweden. * Be female and at least 18 years old. * Have access to and be able to use a smartphone (iOS or Android) compatible with the MELIORA app. * Be willing and able to use the MELIORA app for the entire study duration. * Willing to provide informed consent to participate in the study. * Have completed primary treatment for breast cancer (surgery, chemotherapy, radiotherapy, immunotherapy, targeted therapy, etc.) and currently be in remission. * Be considered "cancer-free" according to their treating physician and may enter the study immediately following this diagnosis. * Ongoing adjuvant hormone therapy is permitted. * Have at least one of the following behavioural or metabolic risk factors for BC, assessed in a random order (each site may determine the order that is most convenient for them) until eligibility is confirmed. If a risk factor is identified, the subsequent assessments can be skipped: * Increased alcohol consumption: More than 1 drink per day. * Increased body mass index (BMI): BMI ≥ 25 kg/m² or waist circumference ≥80 cm for normal weight individuals. * Physical inactivity: Not meeting World Health Organization (WHO) guidelines of at least 150 minutes of moderate-intensity or 75 minutes of high-intensity aerobic exercise per week during the past month. * Suboptimal diet: Low diet quality based on the rapid Prime Diet Quality Score Screener (rPDQS). Exclusion Criteria: MELIORA-HEALTHY study participants will be excluded from study participation if they meet any of the following criteria: * Inability to provide fully informed consent. * Inability to understand or communicate in the local language i.e. Greek in Greece, Lithuanian in Lithuania, Spanish in Spain. * Current or past diagnosis of cancer or other uncontrolled chronic diseases (e.g., cardiovascular disease, diabetes) that affect lifestyle, dietary habits, or communication skills. * Mental illness or disorders that affect lifestyle, dietary habits, or communication skills. * Use of medication that affects lifestyle, dietary habits, or communication skills. * Recreational drug use. * Pregnancy, lactation, or intention to become pregnant shortly before, during, or after the intervention. * Participation in another clinical trial or program aimed at promoting behavioural changes or weight loss at the time of recruitment. If subjects already use health-related apps that affect their weight and lifestyle, including dietary habits and physical activity, the research team will ask them to pause their use until the end of the 12-month study period. However, the use of these applications by the participants cannot be controlled. MELIORA PATIENTS and MELIORA SURVIVORS study participants will be excluded from study participation if they meet any of the following criteria: * Inability to provide fully informed consent. * Inability to understand or communicate in the local language (i.e., Lithuanian in Lithuania, Spanish in Spain, Swedish in Sweden), unless appropriate translation support is available to ensure full understanding of study procedures and informed consent. * Current or past diagnosis of cancer (other than breast cancer, except skin cancer treated with