Brain aging is highly correlated with deficiencies in glucose metabolism. Ketone beta-hydroxybutyrate (d-βHB) may represent an alternative fuel for energy metabolism in brain aging. This study assesses the neurochemical effect of an acute administration of d-βHB in the healthy human brain using MR spectroscopy. Results show that levels of GABA and Glu were significantly reduced in the posterior cingulate region after administration of d-βHB, but not glucose. Additionally, older age significantly predicted higher decreases in levels of both GABA and Glu. This suggests that administration of d-βHB alters normal cerebral metabolic profile in physiological brain aging.