Composition of weight loss in morbidly obese patients after gastric bypass

Bariatric surgery: impact on body composition after Roux-en-Y gastric bypass

BACKGROUND

The aim of this study was to analyze the impact of bariatric surgery on the body composition of patients suffering from class III obesity at different postoperative time intervals.

METHODS

The body composition of 114 patients undergoing Roux-en-Y gastric bypass surgery was measured prior to surgery (T0) and then 30 (T30) and 180 (T180) days following surgery. Body composition was evaluated using the following parameters: total body mass, body mass index, excess weight, percentage of excess weight loss, relative body fat (%F), lean body mass (LBM), and fat tissue mass (FTM). To determine these variables, validated formulas and equations proper to obese men and women were employed.

RESULTS

A significant reduction in %F (41.5%), LBM (20.3%), FTM (37.9%) was noted at each time interval (p ≤ 0.01).

CONCLUSIONS

Bariatric surgery proved to be effective in reducing total body mass and body fat at every time interval. However, dietary measures emphasizing adequate protein intake may be implemented in order to reduce loss of LBM and, coupled with frequent physical activity, may help curtail the impact the surgery has on morphological variables.

Energy, substrate and protein metabolism in morbid obesity before, during and after massive weight loss

OBJECTIVE

To investigate the effect of surgically induced weight loss on energy, substrate and protein metabolism of morbidly obese patients.

DESIGN

A prospective, clinical intervention study of morbidly obese patients before and after surgical treatment.

SUBJECTS

Eight morbidly obese patients (BMI 47.88+/-7.03).

METHODS

Total energy expenditure (TEE; doubly labeled water method), sleeping metabolic rate (SMR; respiration chamber), body composition (deuterium oxide component of doubly labeled water), substrate metabolism (48 h dietary records, 48 h urine collection and gaseous exchange in the respiration chamber) and whole body protein turnover (primed-continuous infusion of L-[1-13C]-leucine) were measured before, 3 and 12 months after vertical banded gastroplasty (VBG).

RESULTS

The TEE decreased as a result of a decreased SMR (64%) and non-SMR (36%; P=0.001). SMR as a function of fat-free mass (FFM) decreased after weight loss (P<0.05). The physical activity index (PAI), defined as TEE/SMR, was low and was not influenced by weight loss. Protein and carbohydrate oxidation decreased significantly after VBG (P<0.05), although 3 months after VBG protein oxidation did not decrease enough to prevent loss of FFM. The energy used for protein turnover was approximately 24% of SMR and did not change after weight loss.

CONCLUSIONS

Compensatory processes that oppose weight loss of morbidly obese patients exist, as demonstrated by the disproportional reduction of SMR, and a low PAI. Protein turnover is not a major contributor to the disproportional reduction of SMR.

Surgery for obesity

The medical risks of obesity increase exponentially as weight increases, and these risks are reduced by sustained weight loss. Behavior modification and dieting provide an approximately 6% loss of body weight at 1 year. Fenfluramine provides an approximately 8% weight loss at 1 year, which can be doubled to 16% when a drug such as phentermine, which works through a different biochemical mechanism, is added to it. This amount of weight loss is insufficient for many severely obese individuals. It was with these facts in mind that the National Institutes of Health Consensus Conference in 1992 recommended that obesity surgery is an appropriate treatment for patients with a body mass index greater than 40 kg/m2 who had failed in attempts at medical treatment and for patients with a body mass index greater than 35 kg/m2 with severe complications of obesity. Vertically banded gastroplasty and Roux-en-Y gastric bypass are the two operations presently recommended because of their relative safety and effectiveness. This article reviews previous procedures that have provided insight into the mechanisms by which these surgeries cause weight loss. The presently used surgeries and their results also are reviewed because until medical therapy improves substantially, surgery remains the most reasonable treatment option for most morbidly obese patients.

Body composition and surgical treatment of obesity. Effects of weight loss on fluid distribution

Obesity is associated with absolute and relative expansion of the extracellular water compartment (ECW). The effects of substantial and prolonged weight reduction on body water distribution are unknown, however. The authors studied total body water (TBW) by tritiated water dilution, ECW by 35SO4 dilution, exchangeable sodium (Na(e)) by 24Na, and total body potassium (TBK) by 40K whole-body counting in 25 severely obese women (body mass index [BMI] = 48 +/- 7 kg.m-2, mean +/- standard deviation) aged 36 +/- 8 years before and at intervals after gastric restrictive (GR; n = 12) and malabsorptive (MA; n = 13) operations for obesity. Results are compared with a control group of 26 healthy normal-weight women (BMI = 21 +/- 2). Before operation, the obese patients had absolute elevations of all water compartments compared with controls, with significantly higher ratios of Na(e) to TBK (1.17 +/- 0.13 versus 0.91 +/- 0.10; p less than 0.05) and ECW to intracellular water (ICW) (E/I = 0.82 +/- 0.17 versus 0.63 +/- 0.06; p less than 0.05). After weight loss of 52 +/- 20 kg in MA and 47 +/- 19 kg in GR patients (nonsignificant between groups) to a stable level 22 +/- 8 months after operation, there were statistically significant reductions in TBW, ICW, TBK, and Na(e) in both groups, but a significant reduction in ECW only after GR. Adjusting for preoperative weight, duration of follow-up, and rate of weight loss, E/I was greater after MA than GR (1.09 +/- 0.25 versus 0.82 +/- 0.14; p less than 0.05). The elevated preoperative E/I ratio did not normalize with weight loss after surgery, and the response was related to the type of operation. The finding remains to be explained although the increased E/I after MA may reflect mild protein-calorie malnutrition not detectable in the blood. The persistence of elevated E/I with significant weight loss after GR might imply an intrinsic or irreversible imbalance of fluid distribution in obese patients.

Thiamin and vitamin B6 intakes and erythrocyte transketolase and aminotransferase activities in morbidly obese females before and after gastroplasty

To assess the need for postoperative vitamin supplements, intakes and nutritional status of thiamin (B1) and vitamin B6 were studied in 18 female gastroplasty patients who received a placebo or different levels of supplemental vitamins. Postoperative erythrocyte transketolase basal (BA) and thiamin pyrophosphate-stimulated (SA) activities and activity coefficients (AC) correlated significantly with B1 intake. Despite a decrease in apotransketolase, low thiamin intakes were associated with increased AC values during the first 3 months. With return to low B1 intakes following repletion during month 4, the AC values remained normal with low total activities. Both alanine (EALT) and aspartate (EAST) aminotransferase apoenzyme levels declined and AC values increased significantly during the first 3 months. Although the EALT-indices were more sensitive to changes in B6 intake than the EAST-indices, the EASTBA and SA correlated most consistently with the intake. Postoperative dietary intakes of both vitamins were inadequate for maintenance of normal activities of these erythrocyte enzymes. Although B1 intake of greater than or equal to 1.0 mg/day was adequate for maintenance of normal thiamin status in most subjects of this study, supplementation with greater than or equal to 1.5 mg/day is prudent even though it may not prevent the early postoperative loss of apotransketolase. Vitamin B6 intake at the current recommended dietary allowance (1.6 mg) was not adequate to maintain coenzyme saturation of the erythrocyte aminotransferases. Marginal intake of other nutrients may have affected the utilization of both thiamin and vitamin B6.

Riboflavin intakes and status of morbidly obese females during the first postoperative year following gastroplasty

Eighteen women participated in a prospective study to assess the need for supplemental riboflavin after gastroplasty. Three groups of five patients received either a placebo or 0.6 or 1.2 mg riboflavin daily for up to 12 months, except during months 4 and 7 when all participants were given a "one-a-day" supplement containing 1.7 mg riboflavin. Dietary intakes of riboflavin decreased from 1.43 +/- 0.17 mg before the operation to 0.70 +/- 0.07 mg at 3 months, and then increased to 1.02 +/- 0.17 mg by 6 months. Even at 12 months, only 33% of the subjects had dietary intakes greater than or equal to 1.2 mg. All those with total intakes less than or equal to 1.7 mg at 3 months had impaired riboflavin status, as indicated by an erythrocyte gluthatione reductase activity coefficient greater than 1.40 and an erythrocyte riboflavin concentration less than 372 nmol/L. In contrast, 62% of the same subjects had urinary riboflavin excretion in the acceptable range. Supplemental intake of 1.7 mg riboflavin appeared to prevent tissue depletion in all subjects.

Obesity

Over the past 20 years, obesity has represented a significant focus of research conducted in Clinical Research Centers (CRCs) in the United States. This review will focus on the progress in our understanding of the disease that CRC-based research has produced; therefore, the reference list is not exhaustive and consists primarily of CRC-based research. Obesity is defined as an excess of body fat as measured by triceps skinfold thickness. The time of onset of obesity is an important factor; for example, early onset is associated with an increase in the number of fat cells. Weight loss reduces the size but not the number of fat cells. Type II diabetes mellitus is a common complication in obese adults; this condition has been related to fat cell size and, in women, to predominantly upper-body fat distribution. Pregnant obese women and their babies are at risk for a number of problems. Abnormalities commonly found in obese persons include increased plasma lipid levels, hyperinsulinism, increased cholesterol synthesis, high frequency of gallstones, and hypertension. Under a variety of experimental conditions, the only difference in the response of obese and normal weight subjects to food was that the obese subjects appeared to consume more, but other data suggest that the obese may have greater energy needs. Carbohydrate intake has been studied extensively. Metabolic rate increases with over-feeding, especially in response to carbohydrate. Basal metabolic rates are higher in obese adults and rise in response to overfeeding; they decrease after weight reduction. This decrease can be counteracted with sucrose, perhaps because sucrose maintains triiodothyronine levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Sudden cardiac arrest in morbidly obese surgical patients unexplained after autopsy

Sixty sudden and unexpected lethal cardiac arrests, with entirely negative findings on autopsy, were reported among 50,314 morbidly obese patients in the care of surgeons performing operations to achieve weight loss. This represented an extrapolated overall annual mortality rate of 65 deaths per 100,000 patients, about 40 times higher than the rate of unexplained cardiac arrests in a matched nonobese population. Eight sudden deaths occurred while waiting for obesity surgery and 22 had cardiac arrest within 10 days after the operation. Late postoperative deaths (more than 4 weeks postoperatively) occurred in 30 instances. A possible marker of a predisposition for sudden, unexpected cardiac arrest was an electrocardiographic abnormality; namely, a Q-Tc interval prolonged to greater than 0.43 seconds. This feature, present in 29 of 38 tracings, denoted increased susceptibility to malignant ventricular arrhythmias. The perioperative clustering of arrests implicated nonspecific stresses incident to otherwise uneventful operations as triggers of lethal dysrhythmias in the absence of organic cardiac disease. Anoxemia after abdominal surgery is an added hazard. Length of postoperative survival among the late deaths was found to be unrelated to degree of initial obesity or to magnitude of weight loss. Patients who died in the late postoperative phase were still grossly obese (mean weight 114.2 kg). Cardiac weights in patients who died within 10 postoperative days (12 patients) or after an average of 103 days (20 patients) were the same (464 and 469 g, respectively), indicating that myocardial mass had remained intact. The data do not suggest nutritional depletion or lean tissue loss as plausible explanations for the cardiac arrests. Screening and postoperative monitoring for Q-T interval prolongation is indicated. Prophylactic beta-blockade in this vulnerable subset of the morbidly obese population may be instituted in anticipation of obesity surgery. The attendant physiologic stresses should be minimized by appropriate measures.

Nutrition after vertical banded gastroplasty

The authors assessed the nutritional status of 60 morbidly obese patients by determining body composition, using multiple isotope dilution at 13.6 +/- 0.4 months following operation. Body weight was followed for an additional 12.3 +/- 0.8 months. Twenty-four patients lost more than 25% of their preoperative weight and were within 30% of ideal weight (a "good" result). At 1 year they had lost 41.4 +/- 1.8% of preoperative weight and the body mass index (BMI) decreased from 46.7 +/- 1.2 to 27.0 +/- 0.6 kg/m2. Despite rapid weight loss, malnutrition did not develop and their body composition became indistinguishable from that of normally nourished volunteers. Twenty-nine patients had a "satisfactory" result with more than 25% weight loss but were not within 30% of ideal. Their weight decreased by 34.8 +/- 1.0% as their BMI decreased from 55.4 +/- 1.2 to 36.0 +/- 0.8 kg/m2. Seven patients lost less than 25% of their preoperative weight (an "unsatisfactory" result). Malnutrition did not develop in any patient. In the authors' experience, in contrast to other weight reducing operations, vertical banded gastroplasty (VBG) results in rapid weight loss without the concomitant development of malnutrition even in patients who return to normal weight.

Failure rate with gastric partitioning for morbid obesity

One hundred twenty-two morbidly obese patients were selected for gastric partitioning from a multidisciplinary obesity clinic over a 4 year period. Initial early success was not a guarantee against cessation of weight loss or the regaining of lost weight. By emphasizing criteria for success and failure, both from our series and the literature, we showed an alarming increase in the failure rates for this procedure which is predicated on the fact that those lost to follow-up were probably failure patients. Numerous articles in the literature contain inadequate data because they refer to pounds rather than percentage of weight loss, they fail to consider revisions as failures, they do not provide 24 month follow-up data, and they do not take into account the possibility that those lost to follow-up are failure patients. The operation carries mortality and serious morbidity rates of 0 to 3 percent and 4 to 10 percent, respectively, with an average 28 percent weight loss at 24 months and a minimal failure rate of 50 percent. The alarming increase in the number of these procedures being carried out across the continent makes it mandatory for surgeons to accurately collect and register their data until the long-term effects and results are known. Gastric partitioning, although probably not experimental, is still developmental. The widespread use and possibly abuse of these operations may result in discreditation of the surgical approach to morbid obesity which would be unfortunate since it is the only practical method at this time for dealing with the problem.

The effectiveness of gastric bypass over gastric partition in morbid obesity: consequence of distal gastric and duodenal exclusion

Eighty-seven morbidly obese patients were prospectively randomized to two operations: gastric bypass was performed on 42 and gastric partition on 45. Gastric bypass proved to be more effective; gastric bypass patients lost 15% more of their original weight at 12 months and 21% more at 18 months. There were no failures in the gastric bypass group; 28 of the 45 operations failed in the gastric partition group. An additional 60 patients underwent gastric bypass since the completion of the study. In the total series of 147 patients who underwent gastric bypass or gastric partition, there was no mortality, and the surgical complication rate was 12%. Because the gastric pouches and the anastomoses were similar in the two operations, the superiority of the gastric bypass may well be due to a heretofore unexplained effect of distal gastric and duodenal exclusion.