September 2008 Issue

Weight Loss Surgery: Is This the Eve of the Sleeve?
By Kathryn M. Lito, MPH, RD, LD
Today’s Dietitian
Vol. 10 No. 9 P. 56

Vertical gastrectomy has its attractive qualities, including its hunger-suppressing effects, but whether it will be patients’ future procedure of choice may hinge on research proving its long-term success rate.

As the incidence of obesity continues to rise worldwide, weight loss surgery has become a realistic opportunity for many patients seeking a permanent solution. Depending on several factors (eg, patient history, comorbidities, body mass index [BMI], age, surgical preference), patients have a variety of surgical options from which to choose, including the gastric sleeve, formally known as sleeve (or vertical) gastrectomy (SG).

The Story of the Sleeve
SG involves laparoscopic longitudinal resection of the stomach via a complete separation of the greater curvature and fundus from the lesser curvature and antrum. The pylorus remains intact, leaving behind a stomach in the shape of a tube or sleeve (see Figure 1). Reports have estimated the final volume of the gastric tube to be as small as 60 milliliters and as large as 200 milliliters, depending on the surgeon performing the procedure.1 This equates to approximately 2 to 7 ounces of food. By keeping the nerves to the stomach and pylorus intact, stomach function is preserved while the volume is drastically reduced.

Traditionally, SG has been used as either the restrictive component of a more complex malabsorptive procedure known as the biliopancreatic diversion with duodenal switch (BPD-DS) or the first step of a staged approach for weight loss. In the latter, super morbidly obese patients who may not be able to physically sustain the stress of extensive surgery will undergo SG to initiate enough weight loss to allow for a gastric bypass or BPD-DS at a later time. Due to effective and significant weight loss in the short term, many surgeons are now using it as a stand-alone procedure.

Because no intestinal rerouting is involved, SG is considered a purely restrictive procedure. It is unlike other restrictive procedures such as adjustable gastric banding (AGB) and vertical banded gastroplasty (VBG), as these rely on a mechanical device with or without stapling to create a small gastric pouch. Achievement of satiety occurs with distention of that pouch just below the esophagus. With nearly 80% of the stomach removed, SG patients are left with a small capacity for food storage, thus limiting their intake. As patients progress postoperatively, they can eat all types of foods but in much smaller amounts.

An appealing feature of SG is patients’ lack of hunger afterward. The dominating theory regarding hunger cessation relates to the removal of the stomach’s ghrelin-producing fundus. Ghrelin is an orexigenic (appetite-stimulating) peptide hormone whose mechanism in weight loss is unclear. The stomach is the major source of circulating ghrelin, with the fundus containing 10 to 20 times more per gram of tissue than the duodenum, the next richest source. Ghrelin is produced when the stomach is empty and during times of negative energy balance, such as low-calorie diets, chronic exercise, and anorexia nervosa. Many believe this phenomenon partly explains why dieters are so hungry. Concentrations rise before meals, stimulating the appetite, and decrease shortly after food ingestion.2

Langer and colleagues compared postoperative plasma ghrelin levels in SG and AGB patients.3 The researchers found significantly decreased levels in SG patients as soon as day one, and levels remained low and stable at one and six months postoperatively. In contrast, they reported significantly increased levels in AGB patients at equivalent time intervals. They also discovered greater excess weight loss in SG patients compared with the AGB group at one month (29.8% vs. 16.7%, respectively) and six months (61.4% vs. 10.6%, respectively). These findings strengthen the theory that less ghrelin production contributes to superior weight loss.

While further research is needed concerning ghrelin’s role after weight loss surgery, particularly SG, these results are nonetheless making SG an attractive option.  

Sleeve Stats
According to a position statement released by the American Society for Metabolic & Bariatric Surgery in June 2007, approximately 15 published reports in the peer-reviewed literature describing short-term outcomes in SG patients are available.4 In these reports, patients’ BMIs range from 35 to 69 kilograms per meter squared, and excess weight loss ranges from 33% to 83%. Resolution of comorbidities such as diabetes, hypertension, hyperlipidemia, and sleep apnea are comparable with results of other bariatric procedures. No follow-up beyond three years has been reported. 

There is a scarcity of research examining nutritional status after SG. One published case report examines Wernicke’s encephalopathy after SG.4 In it, a combination of factors such as gastric wall edema, dietary noncompliance, and vomiting (one week postoperative) led to thiamine deficiency. The patient was not given intravenous thiamine until the development of symptoms such as loss of consciousness and logical verbal contact, nystagmus, cessation of left foot movement, and loss of sensation. Upon treatment, symptoms resolved within several months. The shortage of data inevitably leads to the following question.

To Supplement or Not to Supplement?
Because SG is a restrictive procedure without intestinal rerouting, many may say that supplementation is not warranted and nutrient deficiencies are unlikely. This is a premature statement, as there are no long-term data to support this. What we can and should do is think about this logically while examining existing evidence. One element to consider is preoperative nutritional status. Several studies in the literature identify preexisting micronutrient deficiencies in obese patients undergoing bariatric surgery, including thiamin, vitamin D, zinc, and selenium.5-8 As Carrodeguas and colleagues state, “The amount of food consumed by obese patients is often overwhelming, but the nutritious value of that food is usually poor. The obese population is often erroneously believed to be ‘well-nourished.’”5

So if a patient has a preexisting deficiency, it is not likely to resolve itself with decreased intake after surgery and without appropriate supplementation and a well-planned diet. 

Another reasonable step is to assess patients’ postoperative anatomical changes. As Jacqueline Jacques, ND, chief of scientific affairs for Bariatric Advantage, explains, the surgical removal of a large portion of the stomach removes many cells that play important roles in nutrition. For example, the vast majority of parietal cells, located mainly in the fundus, are lost. Parietal cells produce gastric acid (hydrochloric acid), an intrinsic factor required for vitamin B12 absorption. An acidic environment is important for optimal usage of nutrients (eg, iron, calcium) and protein digestion. Chief cells, located exclusively in the fundus, are also removed. Gastric chief cells release pepsinogen and rennin, enzymes that break proteins into smaller peptides.

Quantity and quality of nutrient intake are also concerns after weight loss surgery. The vast reduction of the stomach’s holding capacity reduces the quantity of intake, at least in the short term, affecting one’s ability to consume a well-balanced diet. Also, with many patients feeling little to no hunger, the likelihood to go for extended periods of time without eating is feasible unless nourishment is a priority. Also, it is not uncommon for patients to experience nausea, vomiting, and food intolerance afterward. Left untreated, nutritional status may be affected. Nutrients such as thiamin can deplete quickly since the body stores little of it. This knowledge has made it customary in most practices to promptly administer IV or intramuscular thiamin to postoperative patients in all suspected cases.

There are also inherent nutrient and health risks when losing weight, with or without surgery, and changing the macronutrient composition of the diet. Dixon and colleagues explored the association of raised homocysteine concentrations, an independent risk factor for cardiovascular disease, with weight loss one year and two years after LAP-Band surgery.9 After finding that higher concentrations of folate and vitamin B12 are required to maintain normal levels, they recommend regular multivitamin supplementation containing folate (400 micrograms), vitamin B6, and vitamin B12 to prevent the rise of homocysteine.

Also, most patients are instructed to consume a high-protein diet immediately after surgery and may not consume many carbohydrates. Intake of folate-rich foods may be limited during that time. Jeanne Blankenship, MS, RD, research dietitian at the University of California, Davis, points out that the dietary reference intake (DRI) is established for healthy populations and the common standard against which intake is measured. Disease states or changes in metabolism may mean the DRI recommendations are inappropriate. “Take calcium, for example. The 1,000 milligrams per day found in the DRIs is based on an average individual consuming the RDA [recommended daily allowance] for protein, which is around 50 to 60 grams per day. Higher protein intake leads to calcium loss, as does weight loss alone. While the 1,000 milligrams is appropriate for most of the population, someone with a sleeve who is rapidly losing weight and consuming additional protein requires significantly more calcium from dietary and supplemental sources,” she says. 

After taking into account potential preoperative deficiencies, anatomical alterations, food intolerance, suboptimal intake, weight loss, and dietary changes, it’s clear that a well-planned diet and supplement regimen must be in order for SG patients. Until several solid, well-designed studies on nutrient status after this surgery are conducted, it does not seem in patients’ best interest to discount supplementation. In the University General Hospital’s bariatric program, we err on the side of conservatism and encourage supplements similar to those of gastric bypass patients such as complete multivitamins, calcium citrate, iron, and sublingual vitamin B12. The latter nutrients are given prophylactically due to decreased acid production. As with all procedures, blood work should be done at regular intervals to determine whether additional supplements are warranted. We also stress the importance of meal balance (as tolerance to most foods improves) to achieve optimal intake of macronutrients as well.          

Surgery of the Future?       
Many wonder whether SG will be candidates’ future procedure of choice. It is an appealing option for patients with anemia, those requiring anti-inflammatory medications, and those with inflammatory bowel disease who would be contraindicated from having intestinal rerouting. By preserving the pylorus, no dumping syndrome exists, and the incidence of peptic ulcers is minimized. No foreign body is used, no adjustments are needed, and there is an option for a second surgery if weight loss is inadequate. 

On the flip side, there is the risk of leaks and complications from gastric division. Because most of the stomach is removed, it is not reversible. As with all surgeries, soft calories such as milkshakes can be absorbed and hinder weight loss if consumed chronically. One major disadvantage at this time is the lack of evidence indicating that weight loss with SG can be maintained over the long term.10 Although the option for conversion to a second surgery is available, most patients would rather have only one surgery. Also, a major barrier to widespread patient accessibility is insurance coverage. Currently, many insurance companies, such as Aetna and CIGNA, explicitly state that SG is not covered as it is considered “experimental, investigational, unsafe, unproven, or inadequately studied.” Until there are sufficient data to add SG to the list of covered weight loss surgeries, it will be provided only to those who can financially reap its benefits.

While SG is being touted as the latest and greatest surgery, patients must be reminded that it is only a tool. Without sincere lifestyle changes, including dietary adjustments, exercise, behavior modification, and ongoing support, weight loss surgeries can take a patient only so far. Participation in a multidisciplinary program during preoperative, perioperative, and postoperative stages is vital to maintaining weight loss and sustaining behavior change.

— Kathryn M. Lito, MPH, RD, LD, is the program dietitian for the University General Hospital bariatric program in Houston. She has been counseling weight loss surgery patients for more than two years, both preoperatively and postoperatively.


A live sleeve gastrectomy procedure is available through Medline Plus at


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3. Langer FB, Reza Hoda MA, Bohdjalian A, et al. Sleeve gastrectomy and gastric banding: Effects on plasma ghrelin levels. Obes Surg. 2005;15(7):1024-1029.

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6. Carlin AM, Rao D, Meslemani AM, et al. Prevalence of vitamin D depletion among morbidly obese patients seeking gastric bypass surgery. Surg Obes Relat Dis. 2006;2(2):98-103. 

7. Flancbaum L, Belsley S, Drake V, Colarusso T, Tayler E. Preoperative nutritional status of patients undergoing Roux-en-Y gastric bypass for morbid obesity. J Gastrointest Surg. 2006;10(7):1033-1037.

8. Madan AK, Orth WS, Tichansky DS, Ternovits CA. Vitamin and trace mineral levels after laparoscopic gastric bypass. Obes Surg. 2006;16(5):603-606.

9. Dixon JB, Dixon ME, O’Brien PE. Elevated homocysteine levels with weight loss after LAP-BAND® surgery: Higher folate and vitamin B12 levels required to maintain homocysteine level. Int J Obes. 2001;25(2):219-227.

10. Baltasar A, Serra C, Perez N, et al. Laparoscopic sleeve gastrectomy: A multi-purpose bariatric operation. Obes Surg. 2005;15(8):1124-1128.