Authors have continued clinical practice and research of low carbohydrate diet (LCD). The case is 62-year-old men with obesity and type 2 diabetes mellitus (T2DM). For social/sport history, he worked as an administration manager of a large hospital and has been baseball player during 15-62 years old. Regarding medical history, he was on LCD with 96kg and HbA1c 6.0% in 2020. He participated many ballgames March-September 2021. He took oral rehydration solution (ORS) (Pokari Sweat, Otsuka Pharmaceutical) 1000ml/day during Mar-June in rather mild climate, and sports drink solution (SDS) (Body Mainte, Otsuka Pharmaceutical) 2000-3000ml/day during Jul-Sept in severe hot weather. He developed thirsty, polydipsia, polyuria, and fatigue and weight loss in Sept and HbA1c was 14.0%. Treatments started immediately by super-LCD, in which taken food in three meals a day was completely taken pictures by recording diet method. The analyzed carbohydrate amount was 40-90g per day, and LCD meal was effective. Just after LCD was started, blood glucose was normalized soon. HbA1c values were decreased to 10.3% in October and 7.8% in November. Consequently, this case had successful and satisfactory clinical improvement by LCD. Some discussion was described concerning LCD, hydration, ORS, SDS, adequate relationship with sports and so on
