Inclusion Criteria:  - ≥18 years old  - Nutritionally 'high-risk' (meeting one of the below criteria)  Low (≤25) or High BMI (≥35) Moderate to severe malnutrition (as defined by local assessments). We will document the means by which sites are making this determination and capture the elements of the assessment (history of weight loss, history of reduced oral intake, etc.). Frailty (Clinical Frailty Scale 5 or more from proxy) Sarcopenia- (SARC-F score of 4 or more from proxy) From point of screening, projected duration of mechanical ventilation >4 days - Requiring mechanical ventilation with actual or expected total duration of mechanical ventilation >48 hours  Exclusion Criteria:  >96 continuous hours of mechanical ventilation before screening Expected death or withdrawal of life-sustaining treatments within 7 days from screening Pregnant The responsible clinician feels that the patient either needs low or high protein Patient requires parenteral nutrition only and site does not have products to reach the high protein dose group. Not ambulating independently prior to illness that leads to ICU admission (use of gait aid permitted) Lower extremity injury or impairments that prevents them from walking prior to hospital discharge (e.g. amputation, knee/hip injury) Pre-existing cognitive impairment or language barrier that prohibits outcomes assessment Pre-existing primary severe systemic neuromuscular disease resulting in severe weakness pre-ICU (e.g., Guillain Barre) 10 Intracranial or spinal process affecting motor function  11. Patients in hospital >5 days prior to ICU admission 12. Not expected to stay ≥4 days after enrollment