Loss of muscle mass and muscle strength as a result of ageing (sarcopenia) reduces physical functioning and increases the risk of hospital admission. This dissertation reveals that even short hospital stays (5-6 days) can lead to a significant loss of muscle mass (3-4%) in elderly patients following hip surgery. It also found that daily protein consumption by elderly patients who were admitted to the hospital following knee or hip surgery was significantly lower than the recommended daily intake, as 35-40% of the food offered was not consumed. In addition to examining muscle loss and protein intake during hospital admissions, we also studied different strategies to support the retention of muscle mass during illness and the natural ageing p...