Older people represent a large part of the population. Focusing on this population in order to protect them from the health risks they may face during their lifetime, especially undernutrition, is a very important issue. Indeed, undernutrition is a disease state caused by an imbalance in nutritional intake in relation to the body's energy expenditure. With technological advances, biomarker measurement has become more efficient and specific, allowing us to better diagnose undernutrition in the elderly. This article presents a large study on healthy aging. Patients use a mobile application called ICOPE to screen for undernutrition and obtain biological data coupled with digital biomarkers obtained from a system for measuring lifestyle behavioral parameters. Actimetric measurements could be considered as a 'partial' parameter to be integrated with others, closer to physiological conditions.