The present invention provides a composition comprising a mixture of an exogenous ketone body, an exogenous NAD modulator and a methyl donor. Typically, exogenous NAD modulator is an exogenous nicotinamide adenine dinucleotide (NAD) precursor. The present invention also provides a method of using such a composition for treating various clinical conditions, including metabolic disorders and neurocognitive impairments. The compositions of the invention can also be used to improve human performance in various competitive or environmental conditions.