Effect of diet and aging on skeletal muscle phenotype and neuromuscular junction remodeling. (a) Fiber cross‐sectional area (CSA) relative to total fiber CSA for Type I, IIa, IIb, and IIx fibers from the GTN of 16‐ and 26‐month‐old mice on a control (CON) or ketogenic diet (KD). (b) Representative cross‐sectional images (10x objective) from the deep portion of the gastrocnemius of 16‐ and 26‐month‐old mice on the CON or KD. Staining was for Type I (blue), IIa (red), IIb (green), IIx (no stain, black), and laminin (yellow). (c) Proportion of small fibers (<750 μm), (d) total number of enclosed type IIa fibers and mRNA expression of (e) markers of skeletal muscle denervation and (f) acetylcholine receptor subunits from the GTN of 16‐ and 26‐month‐old mice on the CON or KD. Values are expressed as means ± SEM. n = 6 (16‐month CON), n = 7 (16‐month KD and 26‐month CON), and n = 9 (26‐month KD). (#) main effect of age. ($) main effect of diet. (*p < 0.05; **p < 0.01; ****p < 0.0001) comparing CON and KD at 16 and 26 months. (a) p < 0.05 comparing CON at 16 and 26 months. (b) p < 0.05 comparing KD at 16 and 26 months