Chronic Exogenous Ketosis in HFpEF

The goal of this clinical research study is to test what effects a ketone drink will have in people with heart failure with preserved ejection fraction (HFpEF), including on exercise and heart function. Patients with HFpEF often have difficulty exercising, and our goal is to understand whether a ketone drink changes much patients can exercise. The study has three visits, including a baseline visit to assess for study eligibility, and two visits (one after 8 weeks of a ketone drink or a placebo drink, and another one after 8 weeks of whichever drink the participant did not receive the first time).