title: A comparison of diet and exercise therapy versus laparoscopic Roux-en-Y gastric bypass surgery for morbid obesity: a decision analysis model.
abstract: BACKGROUND
  In the absence of randomized controlled trials that directly compare medical versus surgical treatment of morbid obesity, decision analysis is a useful tool to help determine the optimal treatment strategy. Using decision analysis we simulated a trial comparing diet and exercise therapy to laparoscopic gastric bypass surgery to determine which approach resulted in longer life expectancy.
  
  
  METHODS
  A Markov decision analysis model was constructed to evaluate survival after laparoscopic Roux-en-Y gastric bypass surgery compared with a diet and exercise program for a 45-year-old woman with a body mass index (BMI) of 40 kg/m(2). Baseline mortality data were derived from published tables of vital statistics, and the relative risks of death associated with obesity (relative to normal weight) were taken from epidemiologic studies. We assumed that successful surgery resulted in a reduction of BMI to 30 kg/m(2). The baseline assumptions were: an operative mortality of 0.4%; a probability of weight loss after surgery of 80%; a rate of weight loss on a diet and exercise program, 20% at two years; a rate of regain of lost weight, 95% at two years; a relative risk of death for a BMI of 40 kg/m(2), 2.70; and a relative risk of death for a BMI of 30 kg/m(2), 1.51.
  
  
  RESULTS
  The undiscounted life expectancy after surgery was 69.7 years compared with 67.3 years for a diet and exercise program (an absolute increase in life expectancy of 2.4 years, a relative increase in life expectancy of 10.8%). Sensitivity analyses assumed discounting at 5%/y, and showed that surgery was associated with a longer expectation of life when the risk of operative mortality was less than 10%, and when the probability of weight loss after surgery was greater than 4%.
  
  
  CONCLUSIONS
  In a decision analysis model, laparoscopic gastric bypass surgery for morbid obesity was associated with a substantially longer survival than diet and exercise therapy.
authors.affiliation: Department of Minimally Invasive Surgery, Legacy Health System, Portland, OR, USA.
authors.forename: Emma J
authors.initials: EJ
authors.lastname: Patterson
authors.forename: David R
authors.initials: DR
authors.lastname: Urbach
authors.forename: Lee L
authors.initials: LL
authors.lastname: Swanström
mesh_terms: D000328:Adult; D000368:Aged; D000713:Anastomosis, Roux-en-Y; D003661:Decision Support Techniques; D004038:Diet, Reducing; D015444:Exercise; D005260:Female; D015390:Gastric Bypass / Q000379:methods*; D006801:Humans; D010535:Laparoscopy; D008017:Life Expectancy; D008297:Male; D008390:Markov Chains; D008875:Middle Aged; D009767:Obesity, Morbid / Q000601:surgery / Q000628:therapy*; D012306:Risk; D012680:Sensitivity and Specificity; D016019:Survival Analysis; D016896:Treatment Outcome