Does Preoperative Weight Loss Predict Success with Laparoscopic Roux-en-Y Gastric Bypass?

| April 26, 2007

by James N. Lau, MD, FACS; and Myriam J. Curet, MD, FACS Both are with Stanford School of Medicine, Stanford University


Obesity is a well recognized public health epidemic affecting not only the United States, but the world. “This insidious, creeping pandemic of obesity is now engulfing the entire world,” Australia’s Monash University professor Paul Zimmet, Chair of the 10th International Congress on Obesity, said on the opening day of the conference. Mounting evidence now rates obesity, with its multiple comorbid diseases, as the second most preventable cause of death next to smoking in the US.

It is well recognized that established medical means of weight loss, including diet and exercise, have limited long-term success.1 Therefore, bariatric surgery becomes a more accepted treatment for morbid obesity. In the US, the number of bariatric surgeries has increased by almost an order of magnitude from 16,000 surgeries performed in 1992 to 103,000 in 2003.2 This is largely due to the increased awareness of the health risks of morbid obesity, coupled with the public’s acceptance of surgical therapy, especially in the era of laparoscopic surgery. There are several types of procedures for weight reduction. The Roux-en-Y gastric bypass (LRYGBP) remains the gold standard in the US. Fourteen-year follow- up data by Pories, et al., in this country has established persistent weight loss with minimal mortality and morbidity.3

With the sharp increase in the prevalence of bariatric surgery, there has developed a greater awareness of the importance of patient selection as a major component to the success of this intervention. Although most large volume centers are somewhat uniform in their medical preoperative workup, there is no clear consensus as to what should be expected of these patients in terms of preoperative lifestyle changes. This persists despite convincing evidence that optimal results are achieved in compliant patients who are willing to improve diet and exercise patterns postoperatively. 4 Predictors for success, especially in the case of laparoscopic Roux-en-Y gastric bypass, are related to long-term lifestyle changes that patients learn to adopt. Also, it has been demonstrated that the heavier patients are at surgery, the less of their excess weight they are likely to lose.5

LRYGBP remains one of the most technically challenging operations in general surgery. The bariatric surgeon is not only required to possess advanced laparoscopic skills, but he/she must apply these techniques in the most adverse of environments. The morbidly obese patient commonly possesses a thick abdominal wall and a large fatty liver. This hepatic steatosis has a prevalence in the morbidly obese of an estimated 58 percent. 6 LRYGBP requires adequate visualization and exposure of the angle of His at the gastroesophageal junction. A large fatty liver provides a challenge toward this exposure and dissection to create the gastric pouch. Schwartz, et al., suggest that hepatomegaly is responsible for 50 percent of the conversions to an open procedure derived from his study of 600 laparoscopic gastric bypass procedures. 7 There are numerous studies that have contributed to the knowledge that weight loss diminishes liver size.8,9 Colles, et al., have shown the most significant reductions in liver size and abdominal fat by serial imaging to occur at two weeks using a very low energy diet.8 Fris, et al., demonstrate exciting evidence that shortterm weight loss reduces liver size.9 Therefore, it should follow that weight loss prior to bariatric surgery should lend itself to measurable differences in operative complexity.

The purpose of this review is to summarize results of studies investigating the impact of preoperative weight loss on outcomes of bariatric surgery. Two retrospective analyses give the hope of less operative blood loss, less operative time, and increased postoperative weight loss with preoperative weight loss. The one prospective trial did affirm lower operative times, but did not confirm a postoperative weight loss advantage with preoperative preparation. The goal of this review is to provide insight into this controversial subject.


Liu, et al., at the Cleveland Clinic performed a retrospective chart review of 95 patients who had undergone LRYGBP and compared those who had lost weight prior to surgery (n=48) to those who did not have any preoperative weight loss (n=47). Those that had preoperative weight loss lost an average of 4.6 percent of their excess weight loss (EWL) over 2.4 months, while the other group gained an average of 4.8 percent of excess weight over three months. Their findings included an average of 102cc of operative blood loss with the preoperative weight gain group versus 72cc for the preoperative weight loss group. Subjectively, the surgeons involved were less likely to report an enlarged liver in the weight loss group. They were also less likely to report a deviation from the standard LRYGBP in the weight loss group.10

Alvarado, et al., at Stanford also presented a retrospective chart review of 90 patients comparing those that lost weight prior to surgery to those that did not. All patients were encouraged to lose 10-percent EWL prior to surgery. All patients underwent LRYGB and were followed up to one year postoperatively. There were no conversions to open procedures. At 12-month follow-up, 86.9 percent of comorbid factors had been corrected or improved. Preoperative weight loss correlated significantly with postoperative weight loss even after accounting for age, gender, and comorbid factors. An increase of one percent of preoperative weight loss correlated with an increase of 1.8 percent of postoperative EWL at one year (P<0.05). Preoperative weight loss of greater than or equal to five percent correlated with a decrease in operative time of 36.2 minutes. Age, gender, total number of comorbidities, number of complications, and resolution of comorbid disease did not correlate with EWL.11

Alami, et al., at Stanford performed the only prospective randomized study of 100 patients prior to bariatric surgery. They ended up with 26 patients in the weight loss group and 35 in the non-weight loss group. The randomization prior to consult resulted in 29 percent of the patients either dropping out of the Stanford program prior to surgery or being excluded from the study prior to sur-gery. Of the patients excluded, the most common reason was the patient’s eventual decision to undergo laparoscopic adjustable gastric banding. Three patients who were randomized to the weight loss group did not have surgery because of the weight loss requirement, and one of those three patients elected to have her surgery at another center that did not have a preoperative weight loss requirement. Those in the weight loss group had a goal of 10 percent EWL prior to surgery. All patients, regardless of randomization, had an average of five months from initial visit to surgery. There was no increase in time to operation in those patients who lost weight. The mean preoperative weight loss was 23.5 pounds, representing an average 8.2 percent EWL. The groups were similar in demographics. There were no differences in postoperative morbidities or mortalities. There were also no differences found in hospital length of stay or conversion rates. The operating rooms times were higher in the nonweight loss group (257.6+27.8 minutes vs. 220.2+31.5 minutes, p=0.0084). At three-month follow-up, the percent of EWL was greater in the preoperative weight loss group (44.1 vs. 33.1, p=0.0267), but that evened out at the six-month followup with no significant difference (53.9 vs. 50.9).12

Fris has shown that patients placed on a 456cal/day (a very low energy) diet for two weeks had significantly smaller livers.9 He used ultrasound measurements of the left lobe of the liver and body analysis at the start of the diet and again prior to gastric banding (two weeks) in 50 patients. The average weight loss of his 50 patients was prior to surgery was 4.1 percent EWL. Since institution of this regimen, he has not encountered any enlarged or fibrotic livers. Experience with patients in his study and others undergoing drastic diets have confirmed the safety of such an acute preoperative weight loss.8-15 Numerous studies have shown that liver size reduces with weight loss of this type.8-10 But, there remains no objective evidence that surgery is easier with a smaller liver. The studies by Liu, et al., Alvarado, et al., and Alami, et al., hints at improved intraabdominal exposure may be related to the amount of preoperative weight lost.10-12 In the paper by Liu, et al., they propose that patients will probably continue to benefit from preoperative weight loss beyond 10 or 20kg by improved exposure from decreased liver size and visceral adipose. 10 The measurements of visceral adipose tissue (VAT) area, body weight, and liver volume by Colles, et al., demonstrate no significant decrease in liver volume from 2 to 12 weeks of a very low energy diet (VLED).8 What is hopeful about their measurements is that weight and VAT area do not seem to plateau until the twelfth week of this diet. The observations by Fris and Colles show that two weeks of a VLED with dietary substitutes show a significant change in liver size to assist in bariatric surgery exposure.8,9 Therefore, the current mandated periods of dietary counseling of 6 months to 3 years by some insurance carriers seems overstated, while a two-week preoperative weight loss and counseling period becomes a more reasonable approach. Perioperative mortality and morbidity for obesity surgery is so low now that a randomized trial comparing surgery alone with surgery that is combined with preoperative weight loss would need to include thousands of patients to show a significant difference. Along the same lines, hospital stays for obesity surgery have leveled off to such a low level that it would similarly be difficult to show a statistically significant difference between surgery alone and surgery combined with preoperative weight loss.

Successful bariatric surgery in the form of optimal weight reduction also requires significant lifestyle changes. Best results are obtained with compliant patients who are willing to modify their diets and to exercise postoperatively.4 Studies suggest that durable weight loss is more dependent on dietary changes than surgical factors.14 The traditional reasons to encourage patients to lose weight preoperatively had been to: 1) introduce patients to restriction of food intake; 2) test the patients’ motivation; and 3) increase total weight loss. The thought was that future results could be improved by past practice. Patients with preoperative dieting and vertical banded gastroplasty (VBG) lost more weight compared to surgery alone in the study by van de Weijgert, where patients were mandated 50 percent EWL prior to VBG and RYGBP.14 Their GBP patients did not show a difference with preoperative dieting of percent EWL. Alvarado, et al., has shown in a retrospective analysis that those with an increase of one percent of preoperative weight loss had an increase of 1.8 percent of postoperative EWL at one year.11 Alami, et al., was able to show at three months post LRYGBP that percent EWL was greater in the preoperative weight loss group (44.1 vs. 33.1, p=0.0267) but that at six months there was no significant difference between those that lost weight preoperatively and those that did not (53.9 vs. 50.9).12 Jamal, et al., show no difference in outcomes with insurance-mandated preoperative dietary counseling and, in contradiction to our findings, the group without preoperative diet counseling had a larger percent EWL at one year.16 To prove the intuitive notion that preoperative weight loss prepares the patient for postoperative dietary changes and good exercise habits, of course, requires a large prospective randomized controlled trail.


Very low energy diets that contain about 450 calories a day can provide safe, acute preoperative weight loss prior to bariatric surgery.8,9,13,14 The weight loss can continue up to 12 weeks, but optimum conditions of liver size appear to plateau after two weeks.8 Weight loss by dietary or just preoperative counseling can make a difference in postoperative percent of EWL.11 Operative times may be faster if preoperative weight loss is over five percent EWL.11,12 Blood loss may also be less with preoperative weight loss.10 Currently, there is no difference shown in morbidity, mortality, hospital stay, and decrease in morbidity- associated diseases whether there is preoperative weight loss or not.10–12,14 There is some evidence that preoperative weight loss predicts better overall weight loss after surgery. 11,12 With the different choices of programs in the US offering bariatric surgery, those that do not or can not lose weight preoperatively may select programs that do not possess stringent preoperative weight loss requirements.12 Bearing this in mind, while lauding those benefits of preoperative weight loss, the optimal approach might be to recommend weight loss prior to LRYGBP, but not to make it a strict requirement.

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Insurance-mandated preoperative dietary counseling
does not improve outcome and increases
dropout rates in patients considering gastric
bypass surgery for morbid obesity. Surg Obes
Relat Dis 2006;2:122–27.
Myriam J. Curet, MD,
FACS, is Professor of
Surgery, Associate
Residency Program
Director, Associate Dean
for Medical Education,
Stanford School of
Medicine, Stanford
University, Stanford,
James N. Lau, MD, FACS, is
MIS Fellow/Clinical
Instructor, Stanford School
of Medicine,
Stanford University,
Assistant Professor of
Surgery, University of Nevada School of
Medicine, Las Vegas, Nevada.
James Lau, MD, FACS, Dept. of Surgery,
University of Nevada School of Medicine,
2040 W. Charleston Blvd., Suite 601, Las
Vegas, NV 89102; Phone: 702-671-2369;
Fax: 702-671-2377; E-mail:

Category: Patient Management Perspective

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