title: A Systematic Review and Meta-analysis of the Effect of Gastric Bypass Surgery on Plasma Lipid Levels.
abstract: 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/m(2) (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.
authors.affiliation: Department of General Surgery, King's College Hospital, Denmark Hill, London, UK, SE5 9RS. kirstincarswell@hotmail.com.|Division of Diabetes and Nutritional Sciences, King's College London, London, UK. kirstincarswell@hotmail.com.
authors.forename: Kirstin A
authors.initials: KA
authors.lastname: Carswell
authors.affiliation: Department of General Surgery, King's College Hospital, Denmark Hill, London, UK, SE5 9RS.
authors.forename: Ajay P
authors.initials: AP
authors.lastname: Belgaumkar
authors.affiliation: Division of Diabetes and Nutritional Sciences, King's College London, London, UK.
authors.forename: Stephanie A
authors.initials: SA
authors.lastname: Amiel
authors.affiliation: Department of General Surgery, King's College Hospital, Denmark Hill, London, UK, SE5 9RS.
authors.forename: Ameet G
authors.initials: AG
authors.lastname: Patel
mesh_terms: D002784:Cholesterol / Q000097:blood; D050171:Dyslipidemias / Q000097:blood* / Q000209:etiology; D005230:Fatty Acids, Nonesterified / Q000097:blood; D015390:Gastric Bypass; D006801:Humans; D008055:Lipids / Q000097:blood*; D009767:Obesity, Morbid / Q000097:blood* / Q000150:complications / Q000601:surgery*; D011184:Postoperative Period; D014280:Triglycerides / Q000097:blood
chemical_list: D005230:Fatty Acids, Nonesterified; D008055:Lipids; D014280:Triglycerides; D002784:Cholesterol
keywords: Cholesterol; Gastric bypass; Gastric bypass surgery; Lipidaemia; NEFA; Triglycerides