PROMISS will contribute to the knowledge role of diet, physical activity (and their interactions) and microbiome in appetite, malnutrition and relevant clinical outcomes. It will also look at the role of oral and gut health in appetite, malnutrition and taste/smell perception. These results will then be translated into recommendations for health professionals, in particular dieticians and geriatricians. Doing so, health professionals will benefit from an increased knowledge about nutrition needs of older persons, and will more easily contribute to preventing malnutrition among older persons living at home.