OBJECTIVES: In Japan, real-world evidence regarding impact of obesity on the prevalence of hypertension is lacking. The objective of this study was to investigate the prevalence and treatment status of hypertension in obese patients, with a focus on resistant hypertension. METHODS: This was a retrospective study using a Japanese healthcare database composed of annual health checkup and claims data (MinaCare Co. Ltd.). Subjects aged >=20 years at 2012 health checkup with 2 years (2011/2012) of checkups were selected for the study. Diagnosed hypertensive subjects (ICD-10 codes I10-I15) who were prescribed with antihypertensive medications within 1 year prior to checkup were defined as “treated”. Resistant hypertension was defined as uncontrolled hypertension (SBP/DBP>=140/90mmHg) with 3 classes of antihypertensives including diuretics, or the use of >=4 classes. RESULTS: A total of 462,323 subjects (32% female, 68% male) were analyzed. The age category 40-<50 years accounted for the largest proportion (35%) of the sample. The mean BMI was 21.8/23.7 and the proportion of obese subjects (BMI>=25) was 16.0%/29.9% (female/male). Approximately 10.4% of the subjects were “treated”. For each age, sex, and treatment category, the prevalence of hypertension (defined as SBP/DBP>=140/90mmHg or “treated”) increased with increasing BMI. In particular, males in 40-<50 age category, odds-ratio for the prevalence of hypertension versus BMI 18.5-<25 were 0.601, 3.607, 7.405, 15.445 for BMI categories <18.5, 25-<30, 30-<35, 35-<40, 40-, respectively. The prevalence of resistant hypertension among those diagnosed and prescribed with antihypertensives was consistently higher for obese subjects (vs non-obese) for each sex and age category; in particular, it was 4.1% (obese) vs 8.7% (non-obese) for males in 40-<50 age category. CONCLUSIONS: We demonstrated that prevalence of resistant hypertension as well as that of hypertension increased with increasing BMI using healthcare database in Japan. These results reconfirm the impact of obesity in the treatment and control of hypertension.