Protein intake stimulates muscle protein synthesis. From the standpoint of maintaining skeletal muscle mass with aging, it is important to optimize the adaptive response to food intake. However, a paucity of information is available describing the effects of habitual dietary protein intake (i.e. either high or low amounts of dietary protein consumed on a regular basis), on the subsequent meal-induced stimulation of muscle protein synthesis. An adaptation to a diet of several days or weeks may involve splanchnic and/or skeletal muscle adaptations that may further enhance, or decrease, the amino acid sensitivity of muscle protein synthesis after protein ingestion.