This interventional clinical trial tests whether a doctor-delivered lifestyle counseling program, supported by two personalized digital tools, is feasible and helpful for improving healthy eating and physical activity in older adults (65 years or older) who previously received a liver or kidney transplant.

All participants first receive medical counseling on healthy diet and physical activity. After 12 weeks, they begin using two smartphone apps ("Gamebus" and "Nutrida") designed to support behavior change at home. Each participant acts as their own comparison, and results after starting the apps are compared with their own results before using them.

The main goal is to find out whether participants can safely use the apps and follow the program (for example: staying in the study, using the apps daily, completing weekly tasks). The study also looks at whether the combined approach-counseling plus digital support-can help improve eating habits, physical activity, body measurements, and routine lab values related to metabolic health.

Participants attend three study visits over 24 weeks. At each visit, they complete questionnaires, undergo body measurements and body composition tests, review their recent diet, and receive lifestyle guidance. At the end, the study will help determine whether this digital-supported lifestyle program is practical and acceptable for older transplant recipients.

Inclusion Criteria:

• Age ≥ 60 years
• Liver or kidney transplant received at least 6 months and no more than 25 years prior
• BMI between 21 and 29.9
• Signed informed consent
• Having a personal smartphone
• Stable immunosuppressive therapy in the past 3 months

Exclusion Criteria:

• Significant weight change (>5% of body weight) in the past 3 months
• Combined liver-kidney transplant
• Medical conditions requiring specific diets that may render adherence to the dietary recommendations of the trial unsafe (e.g., chronic kidney disease, inflammatory bowel disease, celiac disease, bariatric surgery, etc.)
• General physical conditions deemed by the investigator to contraindicate safe participation in any of the trial activities (e.g., blindness, vertebral fractures, wheelchair dependence, home oxygen therapy, etc.)
• Adherence to specific dietary regimens for ethical and/or religious reasons that are incompatible with the dietary recommendations of this trial
• Active malignant tumors currently under pharmacological treatment or awaiting surgical treatment (except cutaneous squamous cell carcinomas), or history of malignant tumors within the last 5 years, except for hepatocellular carcinoma
• Psychiatric comorbidities deemed by the investigator to potentially compromise safety and/or adherence, thereby risking biasing the results (e.g., schizophrenia, bipolar disorder, eating disorders, etc.)
• Changes in glucose-lowering or lipid-lowering therapy during the 90 days prior to the enrollment visit
• Active participation in another research or non-research program aimed at lifestyle modification
• Any clinical condition, diagnosed or under diagnostic evaluation, that the investigator considers may compromise safety and/or a priori adherence to the intervention, with a potential risk of altering the study outcomes