BACKGROUND: Although intentional weight reduction improves obesity-related comorbidities, the associations between weight reduction, medication and related costs are rarely studied. This study investigates the long-term effects of weight change on medication for diabetes and cardiovascular disease (CVD) in severely obese subjects. METHODS: In the intervention study Swedish Obese Subjects, 510 surgically and 455 conventionally treated obese patients have so far been followed for 6 y. Changes in the use and costs of medication were analyzed in relation to treatment and weight change. RESULTS: In comparison with controls, larger fraction of surgically treated patients discontinued the use of medication for CVD and diabetes at 2 and 6 y (risk ratios 0.56-0.77). Among subjects not initially on medication, surgery reduced the frequency of started treatments (risk ratios 0.08-0.80). Relative weight loss  10% was necessary to reduce costs of medication for CVD and diabetes among subjects with such treatment at baseline. To reduce initiation of new treatment against the two conditions, weight loss 15% was required. Over 6 y, the average annual cost for diabetes and CVD medication increased by 463 SEK (96%) in subjects with weight loss <5%, and decreased by 39 SEK(8%) in the weight loss group 15%. CONCLUSION: Long-term intentional weight loss is associated with reduced medication and medication costs for diabetes and CVD. The effects appear to be more marked among subjects who are initially on medication for these conditions, whereas greater weight reduction is needed to prevent new subjects from starting on medication. International Journal of Obesity (2002) 26, 184-192. DOI: 10.1038/sj/ijo/0801864 | 
