Developed country diets rich in sugar and fat contribute to obesity by affecting both peripheral organs and the brain's appetite regulation. We assessed how diet composition impacts mice's body mass, cognitive function, and metabolism. Our goal was to investigate how diet affects learning in mice and identify potential brain-regulating metabolites. Mice were fed four diets: standard diet (STAND), high-sugar & high-fat diet (HSD), high-fat diet (HFD), ketogenic diet (KD), and mouse weight and food intake were measured weekly. After 8 weeks of dietary feeding, the IntelliCage system was used to continuously record nose-spoke events during clockwise and counterclockwise tasks. Blood metabolites were analyzed in mouse plasma samples by GC-MS. The body mass of animals fed HSD and HFD was significantly higher after 8 weeks of the experiment compared to STAND and KD. In cognitive function test, diet affected the mice’s learning speed. STAND and KD mice learned significantly faster than HSD and HFD mice. During the re-learning test similar pattern was observed. GC-MS analysis of blood samples distinguished diets by their composition, shown by PCA. Differences in saccharide metabolism have been observed, with different levels of individual sugars in different diets. Our studies have shown that diet composition, and in particular the fat-to-sugar ratio, can influence cognitive function in mice. We also discovered metabolites that differentiate diets, but their role in modulating brain function requires more detailed investigation.