Waist circumference (WC), waist-to-height ratio (WHtR), and waist-to-hip ratio (WHR), even in individuals who have a normal body mass index (BMI), are correlated with cardiovascular events. The aim of this study is to establish the association between obesity and mitochondrial bioenergetics in peripheral blood mononuclear cells (PBMCs). The study included 1584 subjects from the Electricity Generating Authority of Thailand (EGAT) cohort. The mean age of participants in this study was 68.4 years. There was 24.2 % diabetes mellitus (DM) with a mean HbA1c level of 6.8. WC, WHR, and WHtR were associated with decreased basal, maximal respiration, spare respiratory capacity (SRC), and ATP production, whereas BMI was only associated with reduced maximal respiration and SRC. We further stratified the participants into four groups based on obesity classified by WHR and DM status: Non-DM/Non-obese (n = 468), Non-DM/Obese (n = 733), DM/Non-obese (n = 84), and DM/Obese (n = 299). Both obesity and DM were associated with mitochondrial bioenergetic impairment and increased mitochondrial oxidative stress. Interestingly, there was no difference in mitochondrial bioenergetics impairment between non-DM/Obese and DM participants. Our study demonstrated that WC, WHR, and WHtR better reflected underlying mitochondrial dysfunction in PBMCs compared to BMI. Furthermore, obesity was associated with mitochondrial dysfunction to the same degree as DM.