BACKGROUND: Several studies have documented a beneficial short-term effect on lipid profile after Roux-en-Y gastric bypass (RYGB), but there is limited data on long-term changes. OBJECTIVES: To describe long-term (>
10 years) changes in lipid profile after RYGB and to explore the relationship of lipid changes to changes in weight and baseline and demographic parameters. METHODS: The BAROBS study is a prospective observational study post RYGB conducted at three different hospitals. Surgical procedures were performed between 2003 and 2009, and the collection of data was in 2018-2020. Data on lipid profile, weight, body mass index (BMI), percentage of total weight loss (%TWL), and pre- and postoperative type II diabetes mellitus (DMII) was collected at baseline, 1-2, 5, and 10 years post-surgery and was available for 314 of 546 patients in the study. RESULTS: The mean (SD) follow-up was 11.5(± 1.5) years, with a mean reduction of 11.7% for LDL, 29.7% for TG, and 7.7% for total cholesterol compared to baseline. Except for HDL and total-/HDL-cholesterol-ratio, all lipid variables reached their greatest change after 1-2 years with an attenuation of changes at end of study. HDL and total-/HDL-cholesterol-ratio had stable values from 5 to 10 years post-surgery. Lipid profile improved more in patients with greater weight loss. There was a 59% reduction in DMII at end of study, and there was a significant relation between preoperative DMII and long-term lipid values. CONCLUSION: There is an improvement of all lipid parameters after 10 years post RYGB related to both the magnitude of weight loss and the presence of DMII.