A and B, Arterialized venous plasma phenylalanine and, C and D, leucine concentrations pre-1 week and post-1 week of forearm immobilization in healthy young men fed a eucaloric control diet (A and C; CON; n = 11) or a high-fat overfeeding diet (B and D; HFD; n = 9) providing 50% excess energy from fat in the postabsorptive (0 minutes) and for a 3-hour postprandial period following the ingestion of a mixed meal. CON and HFD data were compared within the same statistical test (3-way analysis of variance with immobilization, time, and diet as factors) for each amino acid separately. For phenylalanine, a significant main effect of time (ie, response to mixed meal ingestion; P < .001) was observed, with no effect of diet (P = .34), immobilization (ie, pre vs post; P = .52), or any interactions (all P > .05). For leucine, a significant main effect of time (P < .001) was observed, with no effect of diet (P = .32), immobilization (P = .16), or any interactions (all P > .05).