Figure 2.

Anabolic resistance of muscle protein synthesis rates (MPS) to dietary amino acids exists as a dimmer switch from low to higher levels. Healthy aging muscle has been shown to be quite responsive to the combined stimuli of feeding and exercise in terms of an MPS response (17), but in absence of prior exercise anabolic resistance is detectable (46). Decreasing the physical activity level, which is perhaps exacerbated further when combining increased sedentary behaviors, increases the level of anabolic resistance on MPS (67). Similarly, obesity increases the level of anabolic resistance, regardless of age (3, 74), with the highest level of anabolic resistance on MPS existing in highly catabolic conditions such as end-stage renal disease (4).