OBJECTIVES: Excess weight, measured by a high body mass index (BMI), is associated with the onset of many diseases, which can, in turn, lead to disability and premature death, subsequently placing a significant burden on healthcare services. This study analysed the burden of disease and the direct costs to the Brazilian Unified Health System (Sistema Único de Saúde [SUS]) attributable to high BMI in the Brazilian population. STUDY DESIGN: Ecological study. METHODS: This ecological study had two components: (1) a time-series assessment to analyse the burden of diseases attributable to high BMI from 1990 to 2019 in Brazil; and (2) a cross-sectional design to estimate the direct costs of SUS hospitalisations and outpatient procedures attributable to high BMI in 2019. Estimates from the Global Burden of Disease study and the costs of hospital admissions and outpatient procedures from the Department of Informatics of the Brazilian Unified Health System were used. Deaths, years of life lost to premature death (YLLs), years lived with disability (YLDs), and years of life lost adjusted for disability (DALYs) were analysed. The direct health cost was obtained in Brazilian Real (R$) and converted in international Dollars (INT$). RESULTS: The current study found a reduction in the number of DALYs, YLLs, and deaths per 100,000 population of cardiovascular disease (CVD) attributable to high BMI and an increase in YLD due to diabetes and cardiovascular disease attributable to high BMI from 1990 to 2019. In 2019, high BMI resulted in 2404 DALYs, 658 YLDs, 1746 YLLs, and 76 deaths per 100,000 inhabitants. In the same year, INT$377.30 million was spent on hospitalisations and high- and medium-complexity procedures to control non-communicable diseases attributable to high BMI. The states in the South and Southeast regions of Brazil presented the highest total cost per 10,000 inhabitants. CVDs and chronic kidney disease showed the highest costs per hospital admission, whereas neoplasms and CVDs presented the highest costs for outpatient procedures. CONCLUSIONS: High BMI causes significant disease burden and financial costs. The highest expenses observed were not in locations with the highest burden of disease attributable to high BMI. These findings highlight the need to improve current public policies and apply cost-effective intervention packages, focussing on equity and the promotion of healthier lifestyles to reduce overweight/obesity, especially in localities with low socioeconomic status.