Description of Immunosenescence Biomarkers and Nutritional Intervention to Evaluate the Implementation of Digital Tools

Inclusion Criteria (commun for all groups): * Men/women * Minimum 18 years old * Adequate cultural level and understanding of the clinical study. * Agree to participate voluntarily in the study and give written informed consent. Population-specific inclusion criteria: * Overweight/obese population: * BMI 25-35 Kg/m2 * Ability to handle electronic devices for data capture. * Healthy young population: * Between 18 and 25 years old (both inclusive). * Senior population * Over 55 years of age. * Oncology patients * Over 18 years of age. * With a clinical diagnosis of an active tumour process. * Patients who developed severe or persistent COVID-19: * Severe COVID-19: Patients who have suffered from COVID-19 disease and whose symptomatology is considered within the clinical pictures of severity of this disease, which may include: severe pneumonia, acute respiratory distress syndrome (ARDS), presence of respiratory failure (SaO2 \<90% room air) or respiratory rate ≥ 30 breaths per minute, sepsis, septic shock, thromboembolism and multi-organ dysfunction (including acute cardiac and renal injuries). * COVID-19 persistence: Patients who have had COVID-19 disease and who remain with active symptomatology after what is considered the acute phase of the disease, after 4 or even 12 weeks, with symptoms persisting over time. Exclusion Criteria: * Dementia, mental illness or diminished cognitive function that can hinder the subject's participation on the study. * S…