RecruitingDietary supplementFiber Supplementation in Heart Failure With Preserved Ejection Fraction (HFpEF)The study team is studying how increasing dietary fiber, specifically through adding potato starch to participant's diet, may impact the species of bacteria in participant's gut microbiome. The study team also wants to understand if adding potato starch to participant's diet helps these bacteria make more short chain fatty acids, a byproduct the team thinks may benefit participant's health.