The ketogenic diet —high in fat and low in carbohydrates— and intermittent fasting have gained popularity not only for weight management but also for their potential to delay cognitive decline associated with neurodegenerative diseases and aging. However, adherence to these diets remains low due to their restrictive nature and undesirable side effects. Both dietary approaches stimulate hepatic production of ketone bodies, primarily β-hydroxybutyrate (BHB), which serves as an alternative energy source for neurons. Here, we investigated whether BHB supplementation could mitigate AMPA receptor trafficking impairments, synaptic dysfunction, and cognitive decline induced by metabolic challenges such as a saturated fat-rich diet. Our results show that, in cultured primary cortical neurons, exposure to palmitic acid decreases surface levels of glutamate GluA1-containing AMPA receptors, whereas unsaturated fatty acids and BHB increase these levels. Furthermore, physiological concentrations of BHB (1–2 mM) countered the adverse effects of palmitic acid on synaptic GluA1 and GluA2 levels in hippocampal neurons, restoring AMPA receptor-mediated synaptic transmission. In hippocampal slices, BHB also reversed palmitate-induced impairments in excitability and synaptic plasticity (long-term potentiation; LTP). Additionally, daily intragastric administration of BHB (100 mg/kg/day for two months) prevented deficits in recognition and spatial memory induced by a saturated fat-rich diet (49% of calories from fat) in mice. In summary, our findings underscore the significant impact of fatty acids and ketone bodies on AMPA receptor abundance, synaptic function, and neuroplasticity, shedding light on the potential use of BHB as a dietary supplement to counteract cognitive impairments linked to metabolic diseases.