OBJECTIVES: Obesity rates have increased in all ages and both sexes irrespective of geographical locality, ethnicity or socioeconomic status, although the prevalence of obesity is generally greater in older persons and women. In Brazil, affects around 21% of adults, consuming more health care resources as the general population. This study analyzes economic impact of obesity in a health plan. METHODS: A self-administered survey was conducted online for 97,983 beneficiaries. For a sample of 2,188 individuals, using categorical questions, we analyzed nutritional status. The annual costs and use of health care were compared between individuals with and without obesity. Statistical analysis used OpenEpi software, by calculating the relative and absolute frequencies, means and standard deviation. For statistical significance, Chi-square tests (Mantel-Haenszel and Fisher's Exact), when p <0.05. RESULTS: From the sample, 56.6% reported obesity (mean age 59.6 years), 62.4% female, 37.6% male. From the total, 35.4% were under treatment and 45.0% from this group were taken medications. In obesity group, the utilization of health plan was significantly higher than without obesity individuals for visits (p = 0.022, OR 1.18), tests (p <0.001; OR 1.64), and therapies (p <0.001, OR 0.88) but not significant for hospitalizations (p=0.209, OR 6.73). The annual expenditure was US$ 2,360.25 versus US$ 1,925.09 on not obese. Considering the estimated prevalence and the incremental cost, the annual impact of obesity was US$ 1,602,548.77. CONCLUSIONS: The severity of obesity is clear and the economic impact is significant. Comorbidities frequently are present increasing expenses with health services and reducing patient's quality of life and their families. More investment on obesity prevention than observed so far is necessary in order to control the rising of costs.