Protein status modulates the rewarding value of foods and meals to maintain an adequate protein intake

Abstract

Proteins are dietary components that contribute to nutritional needs of the body through the provision of nitrogen and amino acids. Protein status is tightly and continuously controlled to prevent or counteract protein deficiency and to maintain or restore an adequate protein status. Animals learn to detect and avoid diets deficient or devoid in protein or in at least one indispensable amino acid and when given a choice reject these diets. Diets restricted marginally in protein or in one or more amino acids more often induce hyperphagia, interpreted as an attempt to increase protein or amino acid intake and to meet the need for protein and amino acids. The increase in energy intake induced by a low protein diet is compensated for by an increased energy expenditure that restrains the gain in adiposity. The status of protein and/or amino acid insufficiency induced by protein or amino acid restricted diets is characterized by a profile of peripheral and central signals that contribute to modulate peripheral metabolic adaptations and central pathways involved in the control of feeding behaviour. These processes impact on the motivation for food and food choice, with an appetite for protein and/or for the limiting amino acid (s) associated with a reward driven sensitivity to protein and amino acid content of food and diets, which leads to restore or maintain an adequate protein status. In contrast to a protein-restricted diet, high-protein diets are usually reported to decrease food intake in both animals and humans, at least for a transient period, in relation to a reported satiating effect of proteins through activation of anorexigenic pathways.