Background Infantile spasms syndrome (IS) is a type of epilepsy affecting 1.6 to 4.5 per 10,000 children in the first year of life, often with severe lifelong neurodevelopmental consequences. Only two first-line pharmacological treatments currently exist for IS and many children are refractory to these therapies. In such cases, children are treated with the ketogenic diet (KD). While effective in reducing seizures, the diet can result in dyslipidemia over time.Methods Employing a neonatal Sprague-Dawley rat model of IS, we investigated how the KD affects hepatic steatosis and its modulation by a defined probiotic blend. A combination of multiple readouts, including malondialdehyde, fatty acid profiles, lipid metabolism-related enzyme mRNA expression, mitochondrial function, histone deacetylase activity, cytokines and chemokines were evaluated using liver homogenates.Findings The KD reduced seizures, but resulted in severe hepatic steatosis, characterized by a white liver, triglyceride accumulation, elevated malondialdehyde, polyunsaturated fatty acids and lower acyl-carnitines compared to animals fed a control diet. The KD-induced metabolic phenotype was prevented by the co-administration of a blend of Streptococcus thermophilus HA-110 and Lactococcus lactis subsp. lactis HA-136. This probiotic blend protected the liver by elevating pAMPK-mediated signaling and promoting lipid oxidation. The strains further upregulated the expression of caspase 1 and interleukin 18, which may contribute to their hepatoprotective effect in this model.Interpretation Our results suggest that early intervention with probiotics could be considered as an approach to reduce the risk of hepatic side effects of the KD in children who are on the diet for medically indicated reasons.