Critically ill patients that are at extremes of weight are at a higher nutritional risk and have higher mortality rates. A recent International multicenter observational study of 2772 ICU patients from 165 ICUs showed a significant inverse linear relationship between the odds of mortality and total daily calories received. Increased amounts of calories was most important for the BMI < 20 group followed by the BMI 20 -< 25 group and BMI > 35 group with no benefit of increased calorie intake for patients in the BMI 25 -< 35 group. Feeding an additional 1000 kcals almost halved the odds of 60-day mortality in patients with a BMI < 25 or > 35. Similar results were observed for feeding an additional 30 grams of protein per day.