The purpose of this study was to determine the effects of diet and physical activity on skeletal muscle telomere length and mRNA levels of components of shelterin, a six-protein complex that protects telomeres, in mice bred over 52 generations for high wheel running activity compared to control mice. Mice were fed either a regular or high-fat diet and were provided wheel access or kept in cages without wheels for 8 weeks. Telomere length was significantly longer in mice fed a high-fat diet compared to those on a regular diet, but no other differences were observed. There were no differences in mRNA levels of the telomere-protecting shelterin components Trf1, Trf2, Pot1a, or Pot1b for diet, wheel access, or selection. High-fat diet may result in telomere dysfunction in these young mice, but we were unable to support our hypothesis that exercise would modify telomere length or shelterin mRNA levels in these mice.