[Understanding the pathophysiology of malnutrition for better treatment]

Malnutrition results from an imbalance between intake and protein-energy requirements resulting in tissue losses with adverse functional consequences. However, it would be better to speak of "states of malnutrition" rather than "malnutrition". Indeed, the mechanisms involved associate, with varying degrees, intake deficiency and increased needs with different clinical consequences. Adaptation to nutrient deficiency aims at establishing lasting saving conditions by promoting optimization of energy reserve utilization while preserving protein pool. This is achieved by reducing basal metabolism (low T3), by decreasing the secretion of anabolic factors and moderately increasing catabolic hormones. Unlike the previous process, the metabolic response to injury or stress, which will sometime induce major increase in requirements, will have as immediate purpose the defense of the organism. The body will draw sometime substantially in its protein pool to produce the glucose required for example by the immune cells. Stress response stems from both an endocrine response, and an immuno-inflammatory one with the important role of pro-inflammatory cytokines released in response to pathogens and more recently alarmins in response to endogenous stress in the inflammatory phenomena of the stress response and in the resulting malnutrition state. Treatment of these malnutrition conditions will thus differ: promoting anabolism in one case and fighting resistance to anabolism and hypercatabolism in the other.