Major burns lead to a hypermetabolic response that is more dramatic than that identified in any other disease or injury. In addition, major burns increase the metabolic demands of the body, which can lead to severe weight body loss and an increased risk of mortality. The hyper-metabolic response is accompanied by severe catabolism and a loss of lean body mass as well as by a progressive decline of host defenses that impairs the immunological response. The protective functions of an intact skin are lost, leading to an increased risk of infection and protein loss. Therefore, adequate and timely provision of nutritional support is a vital component of the care of critically ill burn patients. In addition, nutrition therapy is important in burn care from the early resuscitation phase until the end of rehabilitation. A careful assessment of the nutritional state of burn patients is also important for reducing infection, recovery time, and long-term results. The nutritional therapy in severe burns has evidence-based specificities that help improve the clinical outcomes. The thumb 25 equation (25 kcal/kg of actual body weight) can be used as an alternative method to estimate the energy requirements of patients with major burns in cases where indirect calorimetry is unavailable or not applicable.