INTRODUCTION: In the recent years, more attention is attributed to the impact of diet on central nervous system function. An increasing number of diseases, including neurological disorders, results from inadequate dietary habits. Diet, however, can affect the function of brain and mental processes in a negative as well as a beneficial way. The diet with well‑documented neuroprotective effects is a high-fat and low-carbohydrate ketogenic diet (KD). METHOD(S): We investigated two type of KD, one of them based on animal (KDA), while the other on vegetable fats (KDB). Both diets were applied to two groups of laboratory animals: mice (129S2/SvPasCrl) and rats (Long‑Evans Rat, Crl: LE) for 6 weeks. CONCLUSIONS: Interestingly, preliminary data indicate a unique anxiogenic action of the KD but only in mice.