Obesity impaired spatial learning/memory ability in C57BL/6 mice and induced oxidative stress in the hippocampus (A–F). Obese mice showed shorter latency to original platform site (A) and lower percentage of time in target quadrant (B) compared to control (C–F). Representative swimming tracks of control group (C), HFD group (D), orlistat group (E) and lorcaserin group (F). (G) Representative staining of dentate gyri of the hippocampus with DHE and Hoechst 3325. Magnification: 50×. HFD mice exhibited a higher level of the hippocampal ROS compared to control. (CC: control diet; HC: high‐fat diet; HO: high‐fat diet + Orlistat; HL: high‐fat diet + Lorcaserin). Values are means ± SEM. (*P < 0.05, **P < 0.01 vs. control diet, #
P < 0.05, ##
P < 0.01 vs. High‐fat diet, n = 6, 12 for each group).