A Systematic Review and Meta-analysis of the Effect of Gastric Bypass Surgery on Plasma Lipid Levels

Background: Obesity-related dyslipidaemia comprises hypercholesterolaemia, hypertriglyceridaemia, low HDL-cholesterol and normal to raised LDL-cholesterol levels. 40 % of morbidly obese surgical patients have dyslipidaemia. Roux-en-Y gastric bypass (RYGB) surgery has many beneficial metabolic effects, but the full impact on plasma lipids has not been clearly defined. Methods: A systematic review of electronic databases (Ovid; Medline; PubMed; Embase) between 1960 and March 2012 was performed using search terms including the following: obesity surgery, bariatric surgery, gastric bypass, cholesterol, lipids, triglycerides and non-esterified fatty acids. A total of 2442 manuscripts were screened. Papers with paired plasma lipid levels around RYGB surgery were included. Exclusions included the following: editorials, dual publications, n < 10, resulting in 75 papers of relevance. A meta-analysis was performed of the effect of RYGB surgery upon plasma lipids at different time points up to 4 years following surgery, using a random effects model. Results: Paired data were available for 7815 subjects around RYGB surgery for morbid obesity with a baseline BMI 48 kg/m² (n = 2331). There was a reduction in plasma total cholesterol and LDL-C from 1 month up to 4 years post-RYGB (p < 0.00001, p < 0.00001). Following RYGB, HDL-C increased from 1 year onwards (p < 0.00001), and triglyceride levels were reduced postoperatively from 3 months up to 4 years (p < 0.00001). NEFA levels were increased at 1 month postoperatively (p = 0.003), but from 3 months onwards did not differ from preoperative levels (p = 0.07). Conclusions: RYGB surgery reverses the dyslipidaemia of obesity. These findings support the use of RYGB in the management of high cardiovascular risk lipid profiles in morbid obesity.