Background: Background: Regarding nutritional therapy for obesity and diabetes, low carbohydrate diet (LCD) has been effective. Case presentation: The case is 61-year-old male with obesity and type 2 diabetes mellitus (T2DM). He has been an athlete for long, and exercised much in hot climate during Mar-Sept, 2021. He often drank much amount of oral rehydration solution (ORS) and sports drink solution (SDS). In late Sept, he felt strong fatigue, weight loss, thirsty, and visited a clinic. He was diagnosed to have severe T2DM with HbA1c 14.0%. Results: He started to take super-LCD and to take pictures of all meals every day. He can continue them perfectly and HbA1c decreased to 10.7% in October and 7.8% in November. He has checked pre-prandial and post-prandial blood glucose, ranging almost 120-200 mg/dL due to LCD continuation. Daily carbohydrate intake amounts were checked, which were 87g, 137g, 81g and 136g. Discussion and Conclusion: His intake of ORS and SDS seemed to be adequate judging from their difference. The clinical course was successful, that was probably due to satisfactory lifestyle, continuing LCD and recording diet method, accumulating picture data of all meal, calculating carbohydrate and calorie intake every day. This case become a significant reference.
