**AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** MUSCLE HEALTH DECLINES DURING AGING.ONE FACTOR THAT MAY IMPACT MUSCLE HEALTH IS THE COMMUNITY OF BACTERIATHAT LIVE IN OUR INTESTINES, BUT STUDIESAIMED AT IMPROVING MUSCLE HEALTH BY TARGETING THE GUT IN OLDER ADULTS ARE SPARSE. THE PRIMARY GOAL OF THIS STUDY IS TO USE A DIET THAT IS ENRICHED IN SOLUBLE FIBER, WHICH IS EXCLUSIVELY UTILIZED BY GUT BACTERIATO MAKE SUBSTANCES THAT CAN IMPACT MUSCLE HEALTH, TO IMPROVE MUSCLE-RELATED MEASURES IN OLDER ADULTS.