To examine the association between changes in BMI categories and health-care expenditures among elderly Medicare beneficiaries using longitudinal data of the Medicare Current Beneficiary Survey (MCBS) 2000-2005. Changes in BMI were (i) Stayed Normal: individuals with a normal BMI at baseline and follow-up; (ii) Stayed Overweight individuals with overweight BMI at baseline and follow-up; (iii) Stayed Obese individuals with obese BMI at baseline and follow-up; (iv) Normal-Overweight: individuals with normal BMI at baseline and overweight BMI at follow-up; (v) Overweight-Obese: individuals with overweight BMI at baseline and obese BMI at follow-up; (vi) Overweight-Normal: individuals with overweight BMI at baseline and normal BMI at follow-up; (vii) Obese-Overweight: individuals with obese BMI at baseline and overweight BMI at follow-up. Ordinary Least Squares (OLS) models on logged Year 3 expenditures were used to analyze changes in expenditures between BMI categories. Overall, 35% Stayed Normal, 34% Stayed Overweight, 18% Stayed Obese, 4% gained weight from Normal-Overweight BMI, 3% gained weight from Overweight-Obese BMI, 5% lost weight from Overweight-Normal BMI, and 3% lost weight from Obese-Overweight BMI. Adjusted models revealed those who Stayed Obese had increased total and multiple expenditure types that were significantly higher than Stayed Normal including total (11%), outpatient (25%), prescription (9%), and medical provider (4%). Compared to Stayed Normal, total expenditures were both 26% higher for Obese-Overweight and Overweight-Obese. The current findings highlight the importance of maintaining a normal BMI in the elderly.