OBJECTIVE: In Italy, the most recent report for the National Institute of Statistics (ISTAT) indicate that 1/3 of Italians are overweight an 1/10 obese, making the problem less dramatic than in the UK, Germany or USA. The objectives of this prospective naturalistic study were to describe direct and indirect costs attributable to the management of overweight and obesity and to identify factors associated with costs of management of subjects with overweight and obese. METHODS: The study included subjects between 18-65 years old with a body mass index greater than 25 (BMI, defined as weight in kilograms divided by the square of height in meters). Our estimates of the direct healthcare costs for the Italian National Healthcare Service (I-Nhs) refer to 399 subjects enrolled at 52 centers and show a significant increase in total and I-Nhs monthly costs with increasing BMI. RESULTS: The increase in the average total monthly costs between overweight (82€), mild (189€), moderate (197€) and severe (233€) obese subjects was borderline significant (P=0.051, Kruskall Wallis test). The increase in the average NHS monthly costs between overweight (47€), mild (128€), moderate (162€) and severe (205€) obese subjects was significant (P=0,02, Kruskall Wallis test). We found no statistically significant difference in out-of-pocket costs (P=0.52). CONCLUSIONS: In few years the cost for the health care management of a cohort of more than 5 millions of obese plus 15 millions of overweight individuals in Italy is likely to become unbearable for the I-Nhs, as it will be for most health systems. Policy makers should give the highest priority to the identification, promotion and implementation of effective integrated programmes for the prevention of obesity and overweight.