Background and Objectives: Here we systematically reviewed and quantitatively analyzed randomized con- trolled trials (RCTs) to compare the important initial outcomes of critically ill adults receiving low- and high- energy enteral nutrition. Methods and Study Design: RCTs comparing low- and high-energy supplementation in critically ill adults receiving enteral nutrition admitted to the intensive care unit for an expected stay of >48 h were included. Abstracts submitted to major scientific meetings were included and the primary endpoint was mortality. The risk ratio (RR) and weighted mean difference (WMD) with 95% confidence intervals (CIs) were the effect measures. Results: Eleven RCTs (3,212 patients) were included. The groups did not differ significantly in mortality (RR, 0.94; 95% CI, 0.80-1.11; p=0.47), infections morbidity (RR 1.09; 95% CI 0.95-1.26; p=0.23), pneumonia morbidity (RR 1.04; 95% CI 0.88-1.23; p=0.68), hospital length of stay (WMD -0.27; 95% CI -3.21 to 3.76; p=0.88), intensive care unit length of stay (WMD -0.32; 95% CI, -1.81 to 1.16; p=0.46), mechanical ven- tilation days (WMD -0.30; 95% CI-1.42 to 0.82; p=0.60). The incidence of gastrointestinal intolerance was sig- nificantly lower in the low-energy group (RR 0.79; 95% CI 0.65-0.97; p<0.05). Conclusions: The initial admin- istration of low- versus high-energy supplements did not impact clinical outcomes except for gastrointestinal in- tolerance in non-malnourished critically ill patients receiving enteral nutrition. The initial administration of high- rather than low-energy may benefit these patients by reducing infections, but this effect might actually be at- tributable to the concomitant high protein intake.