Background: Obesity remains a major clinical and public-health challenge in the United States, contributing to rising cardiometabolic disease and long-term healthcare burden. The COVID-19 pandemic substantially altered physical activity, diet, and access to care, yet nationally representative anthropometric data from the post-pandemic period remain limited. Updated estimates are needed to characterize the current distribution of BMI and to quantify associated metabolic risk. Methods: This study analyzed NHANES 2021-2023 data using survey-weighted methods to generate nationally representative estimates of BMI, obesity prevalence, and demographic disparities. Measured height and weight were used to calculate BMI. Subgroup analyses were conducted by age, sex, and race/ethnicity. To assess clinical relevance, survey-weighted logistic regression evaluated the association between BMI category and diabetes (self-report or HbA1c ≥6.5%), adjusting for demographic and socioeconomic covariates. Results: The analytic sample included 6,337 adults. The nationally weighted mean BMI was 29.1 kg/m2, and obesity prevalence was 39.2%. Obesity was highest among adults aged 40–59 years and among non-Hispanic Black adults. In adjusted clinical models, obesity was strongly associated with diabetes (aOR 5.58; 95% CI 4.31-7.22), and overweight showed a modest elevation in odds (aOR 2.17; 95% CI 1.67-2.86). A multipanel survey-weighted BMI distribution figure illustrates overall and subgroup patterns. Conclusions: This work provides the first nationally representative post-pandemic assessment of BMI and obesity using the resumed NHANES 2021-2023 cycle, demonstrating substantial demographic disparities and clinically meaningful associations with diabetes. These findings emphasize continued population-level surveillance and highlight the need for targeted public health and clinical interventions.