Background and Aim: Assessment of total energy expenditure (TEE) is essential for recommendations for dietary intakes and physical activity in patients with diabetes mellitus as well as healthy people. However, few reports have shown TEE in patients with diabetes, particularly in Asian countries. Therefore, we evaluated accurate TEE by doubly labeled water (DLW) and physical activity level (PAL) in Japanese patients with diabetes mellitus. Methods: We planned to recruit sixty patients with type 2 diabetes and sex- and age-matched twenty nondiabetic subjects as the CLEVER-DM Study at a single university hospital. The current presentation is a part of this study with forty-one patients with type 2 diabetes (DM, 69.9 years, men/women: 23/18) and nine patients without DM (non-DM, 67.2 years, men/women: 2/7). TEE was measured over 14 days by DLW method and PAL was calculated as TEE divided by resting energy expenditure assessed by indirect calorimetry. Results: The numbers of DM patients treated with insulin, oral hypoglycemic agents, and diet/exercise were 13 (31.7%), 20 (48.8%), and 8 (19.5%), respectively. Mean (standard deviation [SD]) level of HbA1c was 6.9 (0.8)% for DM and 5.5 (0.4)% for non-DM (p<0.001). Mean (SD) body mass index was 23.2 (2.9) kg/m2 for DM and 23.1 (1.9) kg/m2 for non-DM. After adjusted for sex, age, fat-free mass, and fat mass, mean TEE was 2150 kcal/day for DM, and 2067 kcal/day for non-DM, and there was no significant difference between two groups, although DM tended to have a higher value (mean difference: 83 kcal/day, 95% confidential interval [CI]: -101 to 267 kcal/day). Mean PAL adjusted for sex and age was 1.68 for DM and 1.63 for non-DM, showing no statistical differences (mean difference: 0.04, 95% CI: -0.07 to 0.15). Conclusion: TEE was comparable between DM and non-DM groups among Japanese. Disclosure K. Kondo: None. K. Morino: Research Support; Self; Astellas Pharma US, Inc., AstraZeneca, Sunstar Inc., CMIC Pharmascience, Kowa Pharmaceutical. S. Tanaka: None. K. Fuse: None. A. Ohi: None. M. Kurihara: None. M. Sasaki: Other Relationship; Spouse/Partner; Terumo, Nestle Japan. F. Katsukawa: Speaker's Bureau; Self; Merck Sharp & Dohme Corp., Sanofi, Astellas Pharma US, Inc. H. Maegawa: Speaker's Bureau; Self; Astellas Pharma US, Inc.. Research Support; Self; Astellas Pharma US, Inc.. Speaker's Bureau; Self; Mitsubishi Tanabe Pharma Corporation. Research Support; Self; Mitsubishi Tanabe Pharma Corporation. Speaker's Bureau; Self; Sanofi. Research Support; Self; Sanofi. Speaker's Bureau; Self; Nippon Boehringer Ingelheim Co. Ltd.. Research Support; Self; Nippon Boehringer Ingelheim Co. Ltd.. Speaker's Bureau; Self; Daiichi Sankyo Company, Limited. Research Support; Self; Daiichi Sankyo Company, Limited, Takeda Pharmaceutical Company. Speaker's Bureau; Self; Takeda Pharmaceutical Company, Novo Nordisk A/S, Eli Lilly and Company.