This study will help to quantify heart and kidney ketone uptake with or without an exogenous ketone salt with or without food intake in middle-aged adults. Participants will have 3 different PET scan to perform :~Fasting without exogenous ketone salt~Fasting with exogenous ketone salt supplement~Post-Prandial with exogenous ketone salt supplement.
Participants will undergo 3 Positron Emission Tomography (PET) scans in 3 different conditions :~Fasting without exogenous ketone salt~Fasting with exogenous ketone salt supplement~Post-Prandial with exogenous ketone salt supplement.