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Division of Nutrition and Metabolic Diseases (M.S., V.S., A.G.), Department of Internal Medicine (V.S., A.G.), and Center for Human Nutrition (M.S., V.S., A.G.), University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75235-9052; and Department of Kinesiology (M.S.), Texas Christian University, Fort Worth, Texas 76129
Address all correspondence and requests for reprints to: Abhimanyu Garg, M.D., Professor and Chief, Division of Nutrition and Metabolic Diseases, Center for Human Nutrition, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, Texas 75235-9052. E-mail: abhimanyu.garg{at}utsouthwestern.edu.
| Abstract |
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Evidence Acquisition: The articles were found via PubMed searches. To review the impact of bariatric surgery on weight maintenance and comorbidities, only articles with a postoperative follow-up of 3 yr or longer were included. The articles on nutritional status had a follow-up of 12 months or longer.
Conclusions: RYGB and GB surgeries lead to substantial weight loss in individuals with morbid obesity. However, significant weight regain occurs over the long term, and according to the only well-designed prospective controlled study, the improvement in comorbidities associated with weight loss mitigates in the long term on weight regain. There is some evidence from a retrospective study that RYGB surgery is associated with a modest decrease in long-term mortality. These results remain to be substantiated by well-designed, long-term, randomized and prospective controlled studies. The mechanisms that lead to weight regain need to be further examined and may include increase in energy intake due to enlargement of stoma and adaptive changes in the levels of gut and adipocyte hormones such as ghrelin and leptin, which regulate energy intake; decrease in physical activity; changes in energy expenditure; and other factors. In addition to weight regain, RYGB surgery is associated with frequent incidence of iron, vitamin B12, folate, calcium, and vitamin D deficiency, which requires regular supplementation and monitoring.
| Introduction |
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25 kg/m2], 32.2% are obese (BMI
30 kg/m2), and 4.8% are morbidly or severely obese (BMI
40 kg/m2) (1). In addition, according to another survey, the Behavioral Risk Factor Surveillance System, conducted from 1986 to 2000, the prevalence of severe obesity has increased twice as fast as the prevalence of obesity (2). Obesity is associated with a number of comorbidities including type 2 diabetes, coronary heart disease, hyperlipidemia, hypertension, sleep apnea, pulmonary dysfunction, ischemic stroke, knee osteoarthritis, gallbladder disease, nonalcoholic steatohepatitis, and certain types of cancer (3, 4). In addition, obesity, specifically severe obesity, markedly lessens life expectancy, especially among younger adults (5).
Diet, exercise, and medical therapy have not been shown to be effective in treating severe obesity in the long term (6, 7). This and the steep rise in prevalence of severe obesity and the introduction of laparoscopic procedures may explain the exponential increase in the number of bariatric surgeries from 13,365 in 1998 to 72,177 in 2002 (8). The various types of bariatric procedures include Roux-en-Y gastric bypass (RYGB), gastric banding (GB), vertical banded gastroplasty (VBG), duodenal switch, biliopancreatic diversion, isolated intestinal bypass, and gastrectomy. Of these, RYGB and GB surgeries are the most commonly performed (9) and will be the focus of this review.
According to a recent metaanalysis on bariatric surgery outcomes (10), the patients who undergo RYGB and GB surgeries lose 61.6 and 47.5% of their excess body weight (actual body weight expected body weight based on height and gender) respectively, and a majority of patients with diabetes, hyperlipidemia, hypertension, and obstructive sleep apnea experience complete resolution or improvement of these comorbidities. However, most of the studies included in the metaanalysis were uncontrolled case series, and patients were followed up for no more than 2 yr. Emerging data, however, suggest some gradual weight regain and return of comorbidities during the long term (11). Therefore, we review the literature on the impact of RYGB and GB surgeries on long-term maintenance of weight loss and improvement in comorbidities and the factors that may lead to weight regain in these patients. We also review the effect of these surgeries on nutritional status and intolerance.
The articles in this review were found via PubMed search engines. Only studies with a postoperative follow-up period of at least 3 yr and in which the patients had achieved their maximum weight loss were considered in the review of the impact of bariatric surgery on weight maintenance and improvement in comorbidities. To assess the impact of bariatric surgery on nutritional status, only studies that followed up patients for at least 12 months postoperatively were included. Because of limited research, we did not apply any entrance criteria on the articles on mechanisms of weight regain in bariatric surgery patients.
| Long-Term Effect of RYGB and GB Surgeries on Body Weight and Comorbidities |
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Flum and Dellinger (23), in a retrospective cohort study from Washington, reported a modestly lower mortality rate in morbidly obese subjects who underwent RYGB surgery, compared with a nonoperated cohort of patients with morbid obesity at 15-yr follow-up. This study had a number of limitations. RYGB patients were significantly younger (43 vs. 47 yr, respectively) and more likely to be female (81 vs. 64%, respectively) than the controls. This may have partly accounted for the difference in mortality between the two groups. Factors such as race/ethnicity and degree of obesity, which affect mortality, were not reported. In addition, there was a substantial dropout rate in both the groups. Because this study was retrospective and the data were derived from the Hospital Abstract Reporting System and Vital Statistics databases, the information may be subject to errors. The authors also could not separate patients who underwent the open surgery vs. laparoscopy. The RYGB laparoscopic procedure is associated with lower incidence of incisional hernia than the open procedure (24).
In a retrospective cohort study, MacDonald et al. (22) compared morbidly obese type 2 diabetic patients who underwent RYGB surgery with type 2 diabetic controls who did not undergo surgery. The two groups were matched for age, weight, sex, BMI, and prevalence of hypertension. Percent excess weight loss was 62.4% at yr 1 and 50% at yr 14 in the surgery patients. Body weight of the matched patients with diabetes was not reported. The percent of diabetics requiring oral hypoglycemics or insulin decreased in the surgery group and increased in the control group. Mortality rate was lower in the surgery group than in the control group. The limitations of the study include a higher proportion of whites (76.6 vs. 50%, respectively) and a lower proportion of hypoglycemic medication use in patients undergoing surgery than in the controls (32 vs. 56%, respectively), which could have affected the results, retrospective cohort design, and limited sample size. In addition, information on the proportion of subjects who provided follow-up data were not provided.
Sugerman et al. (12) examined the database of patients who underwent RYGB surgery and reported a decrease in percent excess body weight loss from 66% at 1 yr (91% follow-up) to 52% at 1012 yr (37% follow-up). Resolution of hypertension fell over that time, but resolution of diabetes was unchanged, although the value at yr 1012 was not provided. These results are, however, difficult to interpret because of substantially different sample size at each follow-up and lack of a control group. Other uncontrolled case series studies (13, 14, 15, 16, 17, 19) have also reported a decrease in percent excess weight loss or percent weight loss over time after bariatric surgery but provided limited or no long-term data on comorbidities or major endpoints.
Two uncontrolled case series, on the other hand, reported successful long-term weight loss maintenance in RYGB (18) and GB (20) patients over 60 and 72 months, respectively. The validity of the results from these studies, however, may be questioned because the sample sizes decreased by more than 95% by the end of the studies.
In conclusion, RYGB and GB surgeries lead to substantial weight loss, but weight regain over the long term is not insignificant. According to the only well-designed, prospective, controlled study, the improvement in comorbidities seen initially mitigates in the long term possibly because of weight regain. There is also some evidence from a long-term retrospective study that RYGB surgery is associated with a modest reduction in mortality.
| Mechanisms for Weight Regain |
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A possible reason for the increase in energy intake in RYGB patients may be due to dilatation of the gastric pouch and gastrojejunal anastomosis (26, 27). Late pouch dilatation has been reported in patients who undergo laparoscopic GB surgery (28) and is the leading indication for conversion of GB to a RYGB (29) but is seen less frequently after RYGB surgery (30). Revision surgery to correct these changes leads to improved weight loss (28, 29). However, these complications have been described in only a handful of patients, implying that other factors may be involved in modulating weight regain after bariatric surgery.
Regular physical activity is an important factor in weight loss maintenance (31). According to one survey in RYGB patients with a mean follow-up of 7 yr, successful patients (those who maintained at least 74% of their initial weight loss) exercised regularly (no details given) (32). In the prospective study by Sjostrom et al. (11), the approximate proportion of bariatric surgery patients who reported being active at work changed from 70% at baseline to 90% at yr 1 and 80% at yr 10. The proportion of patients who were active during leisure time was 55, 90, and 80%, respectively. The difference in the proportion active at work and during leisure time between the surgery patients and controls was narrower at 10 yr than at 1 yr. This may explain some of the observed weight regain seen in the surgery patients. Also physical activity may be overreported and thus needs to be assessed objectively. Whether increased physical activity in bariatric surgery patients is effective in weight loss maintenance remains to be proven by randomized trials.
Several studies have assessed metabolic rate in bariatric surgery patients (33, 34, 35, 36). van Gemert et al. (35) and Buscemi et al. (33) found a decrease in resting (33) or sleep (35) metabolic rate, even when expressed per kilogram fat-free mass, with weight loss in subjects who were followed up for 12 or 3642 months, respectively, after surgery. Das et al. (36) and Flancbaum et al. (34), however, did not observe these changes at 14 and 24 months, respectively. Thus, the role of changes in energy expenditure in weight loss and maintenance needs to be studied more thoroughly.
The changes in energy intake, and perhaps even energy expenditure, seen after bariatric surgery may be affected by alterations in gut and adipocyte hormones. Gut hormones such as ghrelin, peptide YY (PYY), and glucagon-like-peptide (GLP)-1 have an important role in governing satiety (37). Of these, ghrelin is an orexigenic peptide, secreted primarily by the enteroendocrine cells in the fundus of stomach and acts through the hypothalamus (38, 39, 40, 41). Ghrelin levels have been found to increase after GB surgery (42, 43), although transiently in the case of one study (43), and suggest a role in weight regain after this procedure. Weight loss in RYGB surgery patients, however, is associated with a decrease in ghrelin levels, compared with weight loss after GB, biliopancreatic diversion, or conventional weight loss treatment (44, 45, 46, 47), and has often been considered to contribute to the marked efficacy of the RYGB, compared with the other procedures. This finding has, however, not been universally observed (48, 49). The conflicting data may be due to the different surgical techniques that affect the functional integrity of the gastric fundus from which ghrelin is mostly secreted. Whether the changes in ghrelin levels in bariatric surgery patients are maintained in the long term needs to be evaluated.
PYY secreted primarily by the more distal intestines in response to nutrient contact and GLP-1 secreted by the intestinal L cells induce satiety (50, 51, 52, 53). Clements et al. (54) reported no difference in fasting GLP-1 level 12 wk after RYGB surgery, compared with preoperative value. In weight-stable RYGB patients with an average follow-up of 35 months, fasting serum PYY level was similar to that of BMI-matched controls, but the PYY response to a test meal (320 kcal) was greater (55). Similarly Borg et al. (48) reported no change in fasting serum PYY and GLP-1 values but increased PYY and GLP-1 response to a test meal (420 kcal) at 6 months after RYGB surgery. The responses to a test meal suggest a beneficial effect on weight loss. It is possible that these changes gradually revert to presurgical levels and contribute to increased energy intake in the long term. Only long-term prospective studies can elucidate the influence of these hormones on energy balance.
According to a number of case series, serum leptin levels decreased with weight loss after bariatric surgery (56, 57, 58, 59, 60). The decrease was beyond the expected value based on body composition (57, 60). In a case-control study, serum leptin levels were lower in weight-stable RYGB patients 35 months after surgery, compared with BMI-matched controls (55). Given the putative adipostatic role of leptin, it is possible that relative hypoleptinemia may play a role in weight regain. Observational studies with very limited sample sizes, however, do not support the hypothesis that relative hypoleptinemia predicts weight regain in moderately obese or overweight subjects who lost modest amount of body weight (812 kg) (61, 62). Nevertheless, leptin administration in weight-stable subjects who lost weight via a liquid formula diet resulted in return of energy expenditure to preweight-loss levels (63). Information on energy intake was not reported (63).
| Effect of Bariatric Surgery on Nutritional Status and Intolerance |
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Deficiency of iron, vitamin B12, folate, calcium, and vitamin D has been frequently observed after RYGB surgery. Deficiency of vitamin A has also been observed, although less frequently. Nutrient deficiencies after GB surgery are less common because it does not have a malabsorptive component, and an adult multiple vitamin and mineral supplement is considered sufficient to prevent these problems (64). Reviewed below are the studies that have reported nutritional deficiencies in RYGB surgery patients (Table 2
). The majority of these studies were uncontrolled case series, and so it is important to note that the studies may have somewhat overestimated the effect of surgery on nutritional status, especially given that nutritional deficiencies have been noted in severely obese subjects before surgery (65) and that many of the patients are menstruating women who are more likely to have poor iron status.
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Serum folate deficiency has been reported to be as high 38% after RYGB surgery (67). Brolin et al. (74) reported that a supplement containing 400 µg of folate per day consistently corrected low folate levels in patients who underwent RYGB surgery, although 1000 µg/d have been recommended by others (64). Primary reason for folate deficiency is decreased folate intake. Malabsorption may not play a big role, even though folate is preferentially absorbed in the proximal part of the small intestine, because absorption can occur along the entire part of the small intestine with adaptation after surgery (76). Maintaining adequate folate levels is important, however, because of the possibility of megaloblastic anemia. Also, there have been reports of neural tube defects in infants born to mothers who underwent RYGB surgery (77, 78).
Calcium and vitamin D deficiency may occur in patients who undergo RYGB surgery, and a deficiency rate of 10% for serum calcium and 51% for serum 25-hydroxy vitamin D levels has been reported (66). PTH levels, however, were not reported (66). Possible contributors to calcium deficiency in the RYGB patients include malabsorption of calcium because of bypassing the duodenum and proximal jejunum in which calcium is mostly absorbed; intolerance to rich sources of calcium such as milk; and defective absorption of vitamin D because of fat malabsorption. Fat malabsorption is due to the short common channel and delayed mixing of fat with pancreatic enzymes and bile salts as a result of bypassing the duodenum. Deficiency of calcium is not always apparent, however, because of release of calcium from bone. Coates et al. (79) and von Mach et al. (80), who followed subjects for 9 and 24 months, respectively, reported elevated markers of bone turnover and/or decreased bone mass in patients who underwent RYGB surgery, compared with patients who underwent GB surgery (80) or the matched obese controls (79, 80). The higher bone turnover in the RYGB patients, however, may be partly due to the increased weight loss in these patients, compared with the other patients. PTH levels were not different between the RYGB and obese control groups (80) nor did they change over time after surgery (79). Nevertheless, to prevent metabolic bone disease, 12001500 mg/d of calcium and 400 IU/d of vitamin D supplements are recommended (64, 65). These amounts, however, may not suppress serum PTH or bone resorption, and increased supplementation may need to be considered (81). Because of reduced stomach acid content, calcium citrate rather than calcium carbonate is recommended because the latter requires acid for absorption (64, 65). Regular monitoring of markers of bone resorption such as urinary N-telopeptide level and markers of bone formation such as serum osteocalcin level may also be necessary.
Serum vitamin A deficiency has been reported in 10% of RYGB patients (66, 67). Whereas symptoms of vitamin A deficiency are rare in this population, a case study reported xerophthalmia and nyctalopia in a patient after a duodenal switch gastric bypass surgery due to inadequate vitamin A supplementation (82). A contributing factor to vitamin A deficiency in RYGB patients is fat malabsorption. Careful monitoring of serum vitamin A status and supplementation as needed is necessary to avoid a deficiency.
Despite the evidence of nutritional deficiencies, many surgeons do not recommend adequate supplements or evaluate serum nutrient levels (83), and most patients do not comply with the recommended supplement regimen (70). Education of both the physicians and patients is thus necessary to prevent malnutrition after RYGB surgery.
Macronutrient deficiency and intolerance
Protein deficiency, assessed by serum albumin levels, is less common than most other nutrient deficiencies (Table 2
) (66, 67, 68, 69). To consume enough protein, patients should be advised to consume fish, which is better tolerated than meat.
Simple sugar intake, especially added sugars (64), has been reported to cause dumping syndrome in as many as 76% (84) of the RYGB patients. The food rapidly enters the small intestine causing an osmotic load, which leads to movement of fluid from the blood into the intestine (85, 86). Rapid food entry into the jejunum also stimulates a substantial release of peptide hormones (85, 86). Clinical manifestations of the dumping syndrome include gastrointestinal symptoms such as early satiety, nausea, cramps, and explosive diarrhea and vasomotor symptoms such as sweating, flushing, palpitations, dizziness, and an intense desire to lie down (85). The insulin response is exaggerated and causes hypoglycemia (85, 86). To prevent dumping syndrome, patients should avoid consuming fruit juices and foods and drinks with added sugar (64); consume frequent, small, dry meals because water can make the food more soluble; include dietary fiber; increase dietary protein (especially fish and chicken); and modestly increase dietary fat (to delay gastric emptying) (86).
| Recommendations |
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Other weaknesses of many bariatric surgery studies include a lack of information on sample size at each follow-up and a nonstandardized way of presenting data on weight loss. Data analysis should be conducted on subjects with a complete set of data as well as the entire group with missing data replaced by baseline data. To facilitate comparison of weight loss across studies, all studies should provide information on body weight and BMI at each time point. Patient characteristics such as gender, age, socioeconomic status, fat distribution, race/ethnicity, etc. that may determine weight change need to be reported.
The role of energy intake and expenditure, physical activity, gut and adipocyte hormones, and stoma changes in weight regain need to be further elucidated by long-term prospective studies. Effect of exercise on weight loss maintenance in bariatric surgery patients needs to be evaluated by randomized, controlled studies.
Because nutritional deficiencies are common in RYGB patients, aggressive supplementation with iron, vitamin B12, folate, calcium, and vitamin D and regular monitoring of nutrition status are necessary. Careful screening before surgery may help to select patients who are more likely to be compliant to supplement recommendations. Women of child-bearing age should be counseled to avoid getting pregnant while actively losing weight and until the serum nutrient levels are normalized. To prevent dumping syndrome, patients should be encouraged to consume frequent, small meals, avoiding fruit juices and added sugars.
In conclusion, bariatric surgeries have a place in treatment of carefully selected patients with morbid obesity. These patients should be encouraged to increase physical activity to possibly prevent weight regain over the long term and consume vitamin and mineral supplements to prevent nutritional deficiencies.
| Acknowledgments |
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| Footnotes |
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First Published Online September 5, 2006
Abbreviations: BMI, Body mass index; GB, gastric banding; GLP, glucagon-like-peptide; HDL, high-density lipoprotein; PYY, peptide YY; RYGB, Roux-en-Y gastric bypass; VBG, vertical banded gastroplasty.
Received March 13, 2006.
Accepted August 28, 2006.
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system in morbidly obese women after gastric bypass. Obes Surg 13:615621[CrossRef][Medline]This article has been cited by other articles:
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S. Savastano, C. Di Somma, L. Angrisani, F. Orio, S. Longobardi, G. Lombardi, and A. Colao Growth Hormone Treatment Prevents Loss of Lean Mass after Bariatric Surgery in Morbidly Obese Patients: Results of a Pilot, Open, Prospective, Randomized, Controlled Study J. Clin. Endocrinol. Metab., March 1, 2009; 94(3): 817 - 826. [Abstract] [Full Text] [PDF] |
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M. L. Vetter, S. Cardillo, M. R. Rickels, and N. Iqbal Narrative Review: Effect of Bariatric Surgery on Type 2 Diabetes Mellitus Ann Intern Med, January 20, 2009; 150(2): 94 - 103. [Abstract] [Full Text] [PDF] |
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A. V. Mayorov, N. Amara, J. Y. Chang, J. A. Moss, M. S. Hixon, D. I. Ruiz, M. M. Meijler, E. P. Zorrilla, and K. D. Janda Catalytic antibody degradation of ghrelin increases whole-body metabolic rate and reduces refeeding in fasting mice PNAS, November 11, 2008; 105(45): 17487 - 17492. [Abstract] [Full Text] [PDF] |
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J. Fleischer, E. M. Stein, M. Bessler, M. D. Badia, N. Restuccia, L. Olivero-Rivera, D. J. McMahon, and S. J. Silverberg The Decline in Hip Bone Density after Gastric Bypass Surgery Is Associated with Extent of Weight Loss J. Clin. Endocrinol. Metab., October 1, 2008; 93(10): 3735 - 3740. [Abstract] [Full Text] [PDF] |
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M. Riedl, G. Vila, C. Maier, A. Handisurya, S. Shakeri-Manesch, G. Prager, O. Wagner, A. Kautzky-Willer, B. Ludvik, M. Clodi, et al. Plasma Osteopontin Increases After Bariatric Surgery and Correlates with Markers of Bone Turnover But Not with Insulin Resistance J. Clin. Endocrinol. Metab., June 1, 2008; 93(6): 2307 - 2312. [Abstract] [Full Text] [PDF] |
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J P H Shield, E Crowne, and J Morgan Is there a place for bariatric surgery in treating childhood obesity? Arch. Dis. Child., May 1, 2008; 93(5): 369 - 372. [Full Text] [PDF] |
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