Recommendations for protein needs in critically ill obese individuals are controversial and insufficiently researched. Current guidelines suggest protein needs for the critically ill obese be calculated with predictive equations that are based on energy needs data and incorporate accepted body weight adjustment calculations. There are no known studies that evaluate the alterations in protein needs based on body mass index in acute care patients. The purpose of this study was to investigate the relationship between BMI and dietary protein needs as measured by 24- hour urinary urea nitrogen (UUN) test to determine if body weight was significantly associated with measured protein needs. The relationship between measured protein needs and estimated protein needs in obese individuals using ideal body weight (IBW) or adjusted body weight (ABW) calculations was also examined. A retrospective chart review of 150 Veteran Affairs Medical Center patients who had a 24- hour UUN test during a previous admission in the last 5 years was conducted. Exclusion criteria included: less than 19 or greater than 85 years of age, patients receiving hemodialysis, a diagnosis of a gastrointestinal bleed or hepatic encephalopathy at time of urine collection, or insufficient urine volume collection. IBW was calculated using the Hamwi formula and ABW was calculated using the Amato formula. All statistical tests were two-tailed and performed using a significance level of 0.05 using SAS 9.2. Participants were 82 European Americans and 62 African Americans with a mean age 62 (±10.0) years and a mean BMI 26.9 (±7.7) kg/m². Subjects had a mean of UUN 96 (±35.4) gram of protein. In the total group, body weight was significantly (p=0.0012) associated with measured protein needs. In obese patients estimated protein needs based on either IBW or ABW calculations were significantly (p<0.0001) different from measured protein needs. The results of this study suggest that protein needs for critically ill patients are associated with actual body weight. Additionally, predicting protein needs in the obese, critically ill patient using IBW or ABW for may not be appropriate. In this population, protein requirements should be measured rather than estimated using predictive equations.