Background d aims: Optimal nutritional support during the acute phase of critical illness remains controversial. We hypothesized that patients with low skeletal muscle area and density may speci call: benet from early high protein intake. Aim of the present study was to determine the association be tween early protein intake {day 2 '4) and mortality in critically ill intensive care unit [ICU] patients with normal skeletal muscle area. low skeletal muscle area. or combined low skeletal muscle area and density. Methods; Retrospectiye database study in mechanically yentilated. adult critically ill patients with an abdominal (ST-scan suitable for skeletal muscle assessment around ICU admission. admitted fromjanuary Zd to January ZINE [n = T39}. Patients received protocolized nutrition with protein target 1.2 '15 glkg day. Skeletal muscle area and density were assessed on abdominal CTscans at the 3rd lumbar yertebra level using preyiously de ned cutoffs. ResuitS: Di T39 included patients [mean age 58 years, 483 male (65%]. PCHE il score 23], 294 [4%] were admitted with normal skeletal muscle area and 445 {soz} with low skeletal muscle area. Two hundred [45% of the low skeletal muscle area group} had combined low skeletal muscle area and density. In the normal skeletal muscle area group, no signi cant associations were found. In the low skeletal muscle area group. higher early protein intake was associated with lower Elliday mortality [adjusted hazard ratio (HR) per ill gfkgfday {182. 95kt] ELI! _D.Q4] and lower 5month mortality {HR [1.88. 95K] CLTB 'DBSJ. Similar associations were found in the combined low skeletal muscle area and density subgroup {HR DEB, 95%CI {164 D.Q for Billday mortality and HR GED. 95%CI i153 D.93 for E month mortality]. Conclusions: Early high protein intake is associated with lower mortality in critically ill patients with low skeletal muscle area and density. but not in patients with normal skeletal muscle area on admission. These ndings may be a further step to personalized nutrition. although randomized studies are needed to assess causality