The pathological states of burn injuries and acute pancreatitis are associated with hypermetabolic and hypercatabolic states. The objective of the study was to determine energy and protein requirements in these conditions. A transversal analytical study was applied to 18 patients: 10 with mild burn injuries in <5% body surface and 8 with acute pancreatitis. Anthropometric measurements were taken (weight, height, BMI, skin folds), as well as resting metabolic rate through indirect calorimetry (RMR IC), protein catabolism using 24-hour urine urea nitrogen (UUN), and trauma factor (RMR IC/BMR Harris-Benedict equation). The sample was made up of 72.2% men and27.8% women. The study of burn and acute pancreatitis patients was carried out on the average 16.1 ± 13.0 SD and 8.8 ± 2.0 SD days after the onset of the disease, respectively. There were no statistically significant differences in RMR IC since mean energy requirements were 24.4 kcal/kg/d and 23.2 kcal/kg/d in patients with burns and acute pancreatitis, respectively, for both sexes (p>0.05). Total energy expenditure (TEE) was not significant (p>0.05). Acute pancreatitis and burn patients showed mild catabolism and their protein requirement was 1,19 g/ kg/d (p>0.05). The trauma factor in acute pancreatitis patients was 0,91 (p>0.05). In conclusion, patient energy requirement was lower than reported or recommended values in both pathologies under study, whereas protein requirement was lower in burn patients.