Aging is accompanied by a progressive loss of skeletal muscle mass and strength, leading to the loss of functional capacity and an increased risk of developing chronic metabolic disease. The age-related loss of skeletal muscle mass is attributed to a disruption in the regulation of skeletal muscle protein turnover, resulting in an imbalance between muscle protein synthesis and degradation. As basal (fasting) muscle protein synthesis rates do not seem to differ substantially between the young and elderly, many research groups have started to focus on the muscle protein synthetic response to the main anabolic stimuli, i.e. food intake and physical activity. Recent studies suggest that the muscle protein synthetic response to food intake is blunted in the elderly. The latter is now believed to represent a key factor responsible for the age-related decline in skeletal muscle mass. We recently applied contemporary stable isotope methodology with the use of specifically produced intrinsically labeled milk protein to study post-prandial protein handling. Several studies were performed to study dietary protein digestion and amino acid absorption kinetics, as well as the subsequent skeletal muscle protein synthetic response in vivo in humans. In this lecture the concept of anabolic resistance will be introduced and some factors that may be responsible for the development of anabolic resistance will be discussed.