Obesity is a severe problem all over the world. One severe problem with obesity is the increased risk of severe diseases. To prevent obesity-related diseases, many people are undertaking prevention measures. Some people try to manage their body weight using supplement drinks, tablets, and health apparatuses. One type of health apparatus is based on the thermal effect. However, the detailed biological mechanisms of the effects of infrared light have not yet been elucidated. In this study, we attempted to clarify the beneficial effects of far infrared light using high-fat diet-treated mice. We exposed mice to far infrared light for 5 months. Body weights were not significantly different in high-fat diet-treated mice that were treated or not treated with far infrared light. However, body weights in far infrared-exposed control mice tended to increase compared to normal mice in the middle treatment term (from 7 to 15 weeks). In the Morris water maze, the goal time of far infrared light-treated control mice was nominally (but not significantly) shorter than the unexposed controls. Serum triglyceride concentrations were significantly increased in far infrared-exposed control mice compared to the unexposed controls. The levels of nerve growth factor and brain-derived neurotrophic factor protein were not significantly different except for nerve growth factor expression in the cerebellum of far infrared-exposed high-fat diet-treated mice. These results indicated that exposure to far infrared light did not provide clear beneficial effects in obese mice. However, the experimental schedule and methods may need to be modified to obtain clearer results.