Body Composition and Metabolic Changes Following Bariatric Surgery: Effects on Fat Mass, Lean Mass and Basal Metabolic Rate

Background: Bariatric surgery has become the method of choice for weight loss in severely obese patients. While the incidence of obesity and its co-morbidities have been well-documented, less is known about the outcomes of the surgery as it relates to body composition and metabolic changes. Methods: 19 bariatric surgery patients (14 female, 5 male) were assessed for basal metabolic rate (BMR), percent fat, fat mass, and lean body mass (LBM) just prior to surgery and at 1, 3 and 6 months after surgery. Results: Analysis of Variance (ANOVA) using the general linear model indicated significant changes in all measures of body composition for each time period. Linear regression was developed for each of these measures. Of the 39.7-kg weight loss, 26.4 kg (66.5%) was fat mass loss and 13.3 kg (33.5%) was LBM loss. BMR significantly decreased from pre-surgery (2091 kcals) to 1 month post-surgery (1758 kcals), with no significant changes in subsequent time periods. Repeated measures ANOVA for the ratio of BMR/LBM indicated no significant differences for any comparison of time periods (F=2.29, P=.111), suggesting that there is no adaptation of an energy-conserving mechanism in these patients. Conclusion: Bariatric surgery was highly successful in inducing significant changes in body weight (39.7 kg), fat mass (26.4 kg), % body fat (7.9%) but also lean body mass (13.3 kg). The 440 kcal decrease in BMR, while significant, was not greater than expected due to significant decreases in LBM.     

Psychiatric Diagnosis and Weight Loss following Gastric Surgery for Obesity

Background: The authors examined associations between lifetime Axis I and Axis II disorders and weight loss following gastric surgery for morbid obesity. Methods: 44 morbidly obese subjects who had undergone vertical banded gastroplasty (VBG) were systematically interviewed with the Diagnostic Interview Schedule (DIS) and were administered the Personality Diagnostic Questionnaire (PDQ). Subjects were followed-up 6 months post-VBG to determine weight loss. Results: The subjects had a mean ± SD age of 37.7 ± 10.6 years.Their baseline weight was 135.3 ± 28.0 kg and their baseline body mass index (BMI) was 50.0 ± 7.4. 34 (77%) were female. Results of linear regressions show a significant association between baseline BMI and weight loss at 6-month follow-up. After adjustment for baseline BMI, there was a non-significant trend toward increased weight loss in association with alcohol abuse/dependence. Similarly, among our analysis of 41 subjects who had received the PDQ, we found a non-significant trend toward increased weight loss in association with "any" PDQ diagnosis and with antisocial personality disorder/trait after adjusting for baseline BMI. Conclusion: The data suggest that Axis I and Axis II diagnoses were not predictive of weight loss following VBG during a 6-month follow-up.     

Effect of Significant Intermediate-term Weight Loss on Serum Leptin Levels and Body Composition in Severely Obese Subjects

Background: Leptin, produced by adipose tissue, signals body fat content to the hypothalamus. Serum leptin levels (SLL), elevated in obese humans, decrease with weight loss. This study investigated the reduction of SLL and fat mass following restrictive bariatric surgery. Methods: Obese subjects (body mass index [BMI] >35 kg/m², n=154) undergoing gastric banding (weight-reduced subjects) were investigated for SLL and body composition before surgery and for 2 years after. Overweight subjects matched for fat mass and gender (fat mass-matched overweight controls, n=194) and subjects who had never been obese (normal weight controls, n=158) were studied for comparison. Results: SLL were highest in weight-reduced subjects and decreased with weight loss (P <0.001), remaining elevated compared with normal weight controls (P <0.001) but lower than fat mass-matched overweight controls (women: P <0.04). At 2 years, SLL normalized for fat mass (allowing comparison between various levels of adiposity) were lower in weight-reduced subjects compared with fat mass-matched overweight controls (women: P =0.003), yet were similar for weight-reduced subjects at 2 years compared with normal weight controls despite 14 kg greater fat mass. Relative lean mass of extremities in weight-reduced subjects increased with weight loss (P <0.001). Conclusion: SLL decreased after considerable weight loss more than could be accounted for by fat mass or BMI reduction alone. This disproportionate decrease in SLL might point to a mechanism that evolved as adaptation to starvation during times of famine. Thus, post-obese subjects may be at risk of weight-regain due to disproportionately low SLL and increased appetite via the leptin-melanocortin pathway.     

Patient Characteristics Impacting Excess Weight Loss following Laparoscopic Adjustable Gastric Banding

Background: Weight loss is more variable after laparoscopic adjustable gastric banding (LAGB) than after gastric bypass. Subgroup analysis of patients may offer insight into this variability. The aim of our study was to identify preoperative factors that predict outcome. Methods: Demographics, co-morbid conditions and follow-up weight were collected for our 1st 200 LapBand ? patients. Linear regression determined average %EWL. Logistic regression analysis identified factors that impacted %EWL. Result: 200 patients returned for 778 follow-up visits. Median age was 44 years (21-72) and median BMI 45 kg/m² (31-76). 140 (80%) were women. Average %EWL was y % = 0.007 %/day (days since surgery) + 0.12% (correlation coef. 0.4823; P<0.001). %EWL at 1 year was 37%. The best-fit logistic regression model found 7 factors that significantly changed the odds of achieving average %EWL. Older patients, diabetic patients and patients with COPD had greater odds of above average %EWL. Female patients, patients with larger BMIs, asthmatic patients and patients with hypertension had increased odds of below average %EWL. Conclusion: Specific patient characteristics and comorbid conditions significantly altered the odds of achieving satisfactory %EWL following gastric banding.     

Vertical banded gastroplasty in the Aegean Region of Turkey

Background: Obesity is increasing in Turkey. The first experience with vertical banded gastroplasty (VBG) with regular intermediate-term follow-up in the Aegean Region of Turkey is presented. Methods: From November 1993 to August 1999, 40 morbidly obese patients underwent VBG. The patients were evaluated on the basis of excess weight loss (EWL) and satisfaction with the operation. Results: Regular follow-up was obtained in 38 patients (95%), with mean follow-up 27.2 months (14-85). Average preoperative body weight (BW) was 141.4 kg (93-238) and body mass index (BMI) was 52.3 kg/m² (41-77.8). Average EWL was 64.1% (21.2-92.3). Average postoperative BW and BMI were 93.3 kg (70-145) and 34.4 kg/m² (25.1-53) respectively. 35 of 38 patients (92%) lost more than 25% of EW and 28 of 38 (73.6%) lost more than 50% of EW. After weight loss, hypertension disappeared or improved in 86% of patients and diabetes resolved in 75%. Sleep apnea disappeared in 100% of patients. The early and late complication rates were 7.9% and 15.8% respectively. 33 of 38 patients (87%) were satisfied with the operation. Conclusion: VBG was safe and effective, resulted in acceptable weight loss, and the vast majority of patients were satisfied.     

Effects of Weight Loss on QT Interval in Morbidly Obese Patients

Background: Obesity causes structural changes to the heart that may influence its function. Furthermore, morbid obesity is associated with an acquired prolongation of the QTc interval that may lead to potentially hazardous arrhythmias. The present study investigated the effect of body weight loss following vertical banded gastroplasty (VBG) on the QTc interval. Methods: 17 morbidly obese patients, scheduled for elective VBG, were studied before the operation and 8-10 months postoperatively, when each patient had achieved a weight loss of ≥ 25% of the preoperative body weight. Results: 15 patients achieved significant body weight loss of ≥ 25% within the first 8-10 postoperative months (P <0.001).This weight loss, corresponding to an excess weight loss of 48.7% and a mean body mass index (BMI) reduction from 49.7 kg/m² to 36.6 kg/m², was followed by significant shortening of the QTc interval from 428 msec to 393 msec (P <0.001). Conclusions: The significant postoperative weight loss following VBG was accompanied by shortening of the QTc interval. This effect is expected to reduce the incidence of fatal conditions associated with the long QT syndrome, such as malignant ventricular arrhythmias and sudden death, and therefore improve morbidity and mortality.     

Effects of Laparoscopic Gastric Banding on Body Composition,Metabolic Profile and Nutritional Status of Obese Women: 12-Months Follow-Up

Background: Obesity is frequently associated with metabolic and cardiovascular co-morbidities and high mortality rates. Besides, because of the increasingly recognized fact that conservative therapy for morbid obesity is associated with an almost 90-95% failure rate in the long term, and probably because of the development of laparoscopic surgery,the demand for bariatric surgery is increasing rapidly.The significant weight loss observed during the first 6-12 months after gastric banding is related to the severe food restriction, related hypercatabolism, and has a potential risk of mineral and vitamin deficiencies.The aim of this study was to evaluate the effects of gastric banding on total body composition, metabolic profile and nutritional status. Methods: 31 women were studied with median age 36 years (range 25-52), body weight 118.6 kg (range 98-156), BMI 43.6 kg/m² (range 36-56 kg/m²), percentage of excess body weight (%EW) of 107% (range 72- 166%), waist 115 cm (range 98-132) and hip 138 cm (range 119-155). Total body composition was measured before, 6 and 12 months after laparoscopic gastric banding, using dual-energy x-ray absorptiometry. Metabolic and nutritional profile were evaluated before and 1, 3, 6, 9 and 12 months postoperatively. Results: There was a 23.3% reduction of total body weight and 36.8% reduction of body fat. Unfortunately we also observed a reduction of Fat Free Mass (FFM) of 9.6%. In addition, the major determinants of weight loss were the initial body weight and abdominal distribution of fat mass. Reduction of FFM was positively correlated with the rapidity of weight loss. A significant improvement of glucidic profile was observed, with disappearance of impaired fasting glucose, and normalization of the values of triglycerides in all patients. The prevalence of the metabolic syndrome decreased from 89% in preoperative conditions to 15% 1 year after gastric banding. No major nutritional deficiencies was found following gastric banding. Conclusions: This prospective study suggests that the first 6 months postoperatively are crucial for weight loss and changes in body composition. Furthermore, the significant reduction of body weight is accompanied by an important improvement of biological abnormalities.     

Long-Term Weight Loss after Bariatric Surgery in Patients Visited at Home Outside the Study Environment

Background: Bariatric surgery results in sustained weight loss in the majority of patients. The controlled setting of a trial, however, does not necessarily reflect the everyday routine practice. Therefore, to investigate the results of bariatric surgery in a more natural setting, patients were visited at home, outside a study and hospital environment. Methods: Patients who underwent a vertical banded gastroplasty or a gastric bypass between 1980 and 1997 were eligible. Body weight and height were measured. Patients filled out general and health status questionnaires (Nottingham Health Profile (NHP)). Results: Responses were obtained from 236/313 subjects (75%) with a mean ± SD age of 42.9 ± 10.2 years and a mean current body weight of 100.3 ± 20.7 kg. A maximum weight loss of 48.2 ± 18.4 kg or 70.8 ± 22.4% excess weight loss was obtained after 17 ± 15 months, of which 32.1 ± 22.6 kg or 45.2 ± 29.3%, respectively, was maintained at 8.2 ± 4.5 years after the intervention. Males and females did not differ in weight loss. The type of operation had no influence. Age >50 years and a BMI >50 kg/m² were not related to a poor outcome, but a time lapse of >5 years since the operation resulted in a less well sustained weight loss. The subjective health status improved considerably, but less so with a smaller weight loss and longer lapse of time since the operation. Especially in females, the NHP still deviated substantially from Dutch norm values. Conclusions: Surgically obtained weight loss is satisfactory in patients outside a strictly controlled study setting. Health benefits are substantial, but are adversely affected by weight gain and time elapsed since the operation.     

Gallstone Formation after Weight Loss following Gastric Banding in Morbidly Obese Dutch Patients

Background: Obesity is a risk factor for the development of gallstones. Rapid weight loss may be an even stronger risk factor. We retrospectively assessed the prevalence and risk factors of gallstone formation after adjustable gastric banding (AGB) in a Dutch population. Methods: All patients who underwent AGB between Jan 1992 and Dec 2000 for morbid obesity were invited to take part in this study. Transabdominal ultrasonography of the gallbladder was performed in those patients without a prior history of cholecystectomy (Group A). Additionally, 45 morbidly obese patients underwent ultrasonography of the gallbladder before weight reduction surgery (Group B). Results: 120 patients were enrolled in the study (Group A). Prior history of cholecystectomy was present in 21 patients: 16 before and 5 after AGB. Ultrasonography was performed in 98 patients: gallstones were present in 26 (26.5%). On multivariate analysis, neither preoperative weight, nor maximum weight loss, nor the interval between operation and the postoperative ultrasonography were determinants of the risk for developing gallstone disease. Prevalence of gallstones was significantly lower in the morbidly obese patients who had not yet undergone weight reduction surgery (Group B). Conclusions: Rapid weight loss induced by AGB, is an important risk factor for the development of gallstones. No additional determinants were found. Every morbidly obese patient undergoing bariatric surgery must be considered at risk for developing gallstone disease.     

Changes in Liver Histology Accompanying Massive Weight Loss after Gastroplasty for Morbid Obesity

Background: Nonalcoholic steatohepatitis (NASH) is common in morbid obesity. Our goal was to evaluate the alterations in liver histology and biochemistry before and after weight loss in 51 morbidly obese patients following Mason's vertical banded gastroplasty. Methods: Two biopsies were performed (on entry and after an average of 18 months), while 16 of these subjects had a third biopsy 17 months after the second. Results: On entry, steatosis and steatohepatitis (mostly grade 3) were present in 98.0% and fibrosis (mostly stage 2) in 94.1% of the subjects. After an excess weight loss of 66%, steatosis and steatohepatitis improved significantly (P<0.001). Although a significant overall decrease in fibrosis occurred (P=0.002), 21 patients (41.1%) did not change and only 6 patients (11.7%) increased in fibrosis. None developed cirrhosis. The decrease in steatohepatitis was significantly correlated (P=0.011) with the reduction of BMI. Fasting serum glucose, lipids, lipoproteins, transaminases, gamma-glutamyl transpeptidase, alkaline phosphatase and fibrinogen were also significantly improved at the time of the second biopsy. The third biopsy performed in 16 of the subjects showed further significant improvement in liver histology. Conclusion: NASH improved significantly with massive weight loss in non-diabetic, non-alcoholic, morbidly obese subjects, while fibrosis improved in nearly half of the patients.     

Weight Loss Following Vertical Banded Gastroplasty: Intermediate Results of a Prospective Study

Background: Morbidly obese patients who undergo purely restrictive bariatric operations may fail to maintain satisfactory long-term results. In an attempt to achieve the best possible outcome after restrictive procedures, we have employed preoperative selection criteria and are following this selected patient group over time in order to evaluate longterm success. Materials and Methods: From June 1994 through August 2000, 166 morbidly obese patients underwent various bariatric procedures at our institution. Of these patients, 35 underwent vertical banded gastroplasty (VBG) based on selection criteria, including degree of obesity and dietary habits and eating behavior. All patients were seen at 1, 3, 6, 9, and 12 months postoperatively and yearly thereafter. Average follow-up time now is 4.1 years (29-75 mos.), and follow-up is 100%. A multivitamin and mineral supplement is administered to all patients for at least 6 months. Radiology examination is performed in all patients on the 4th postoperative day and at each yearly visit, in order to check for staple-line disruption and stomal stenosis. Results: Early postoperative morbidity was 5.7%. Late postoperative morbidity was 22.8%. A significant number of patients had some degree of stomal stenosis as shown by radiology examination, but to date there has been no need for surgical revision. There has been no early or late mortality.Weight loss results expressed as average percent excess weight loss (% EWL) were as follows: 61% (28-90) at 1 year, 61% (20-90) at 2 years, 57% (13-91) at 3 years, 56% (25-87) at 4 years and 37% (24-59) at 5 years following surgery. A significant number of patients with excellent weight loss had a high frequency of vomiting. Evaluation by BAROS showed that 25% of patients had an overall unsatisfactory outcome. Anemia and iron deficiency were found in 46% and 32% ofVBG patients respectively.Recurrence of preexisting comorbidities was significant if lost weight was regained. Conclusions: In spite of preoperative selection of patients for VBG, a significant percentage of patients had poor overall results in terms of weight loss, quality of life, and resolution of preexisting comorbidities. For these reasons and based on the long-term results published by others, VBG is no longer our preferred surgical option in morbidly obese patients.     

Weight Loss Composition: The Effects of Exercise following Obesity Surgery as Measured by Bioelectrical Impedance Analysis

Background: Sudden weight loss following bariatric operations for morbid obesity, such as the duodenal switch (DS), can result in a concurrent decrease in lean body mass. Several methods for tracking body composition, such as bioelectrical impedance analysis (BIA), are available to monitor these changes. One method to offset the negative effects of sudden weight loss on body mass composition may be exercise. Methods: 100 patients who had undergone the DS operation for morbid obesity were classified as exercisers and non-exercisers based on self-reporting. Their body mass compositions were measured using BIA preoperatively and at 0.75, 1.5, 3, 6, 9, 12, and 18 months postoperatively. Results: At no study interval did postoperative percent changes in weight loss differ between the exercise and non-exercise groups. At 18 months postoperatively, the exercise group showed a 28% higher loss of fat mass and an 8% higher gain in lean body mass than the non-exercise group. Conclusion: Exercise positively influences body mass composition following the DS. BIA can be successfully employed to monitor changes, diagnose deficiencies, and formulate treatment recommendations.     

A Correlation Method for Weight Loss after Gastroplasty

Background: Prevalence of morbid obesity is increasing in western countries. As a consequence, bariatric surgery has intensively developed in the last decades. Someone facing the need for comparison between gastric restrictive procedures could find it useful to have a general expression for weight loss after surgery. Methods: A first approach of this issue can be made, taking into account two simple hypotheses: linear dependencies of weight variation versus sum of energy transfer, and of loss of energy versus weight. With the additional assumption of a constant energy income (the goal of surgery), one can obtain for the weight loss ΔP=P₀-P=(P₀-B)(1-e^-βt), where P and P₀ are the weight at time t and t₀, B and β being adjustable constants. Results: A preliminary study has shown us that most of our weight loss data could be fitted using such an expression. The model was successfully tested on gastric banding and calibrated vertical banded gastroplasty data, but with greater emphasis on laparoscopic vertical banded gastroplasty. Conclusion: We introduce a simple, exponential growth-like function that can be used for the fit of weight loss data of patients who underwent bariatric surgery in our surgical unit. Such a function could also be of practical interest for the survey of weight loss.     

Body Image: Appearance Orientation and Evaluation in the Severely Obese. Changes with Weight Loss

Background: The severely obese experience discrimination and embarrassment regarding their appearance, causing psychosocial distress. We assessed the importance of appearance, presentation and self-evaluation of appearance before and after weight loss, in severely obese subjects (BMI >35 kg/m²). Methods: Appearance orientation (AO) and appearance evaluation (AE) sections of the Multidimentional Body Self Relations Questionnaire were completed by preoperative patients and those attending an annual follow-up after Lap-Band? gastric restrictive surgery over a 2-year period. AO is a measure of the importance one places in appearance. AE is a self-evaluation of one's appearance. Results: Before surgery 322 consecutive patients (48 men and 274 women) completed the survey. AO was similar to that of community norms (mean scores 3.76 ± SD 0.6 vs 3.84 ± 0.6), with the exception of the super obese (BMI >50 kg/m²) who placed significantly less importance on their appearance (3.34, ± 0.8, p=0.001). There was no change in AO at 1-4 years after surgery, with the exception of the super obese whose mean values rose to normal by 1 year. AE was very low before surgery compared with community normal values (1.6 ± 0.6 vs 3.4 ± 0.8, p<0.001). Major improvement in mean AE was seen at 1 year after surgery (n=209, 2.6 ± 0.8, p<0.001) and the improvement was maintained out to 4 years.The change in AE from pre-surgery to 1 year (n=122 paired) correlated positively with the percentage of excess weight lost (r=0.32, p<0.01) and positively with measures of quality of life and psychological disturbance. Conclusion: Major improvements in appearance evaluation occur with weight loss after surgery and this is associated with psychological benefit.     

A Prospective Study of Body Dissatisfaction and Concerns in Extremely Obese Gastric Bypass Patients: 6- and 12-Month Postoperative Outcomes

Background: Body image is a multifaceted construct commonly associated with obesity. This study examined changes in body dissatisfaction, and shape and weight concerns in bariatric surgery patients from baseline to 6 and 12 months post-surgery. Methods: 109 extremely obese patients who underwent gastric bypass surgery completed the Body Shape Questionnaire (BSQ), and the Shape and Weight Concern subscales of the Eating Disorder Examination-Questionnaire (EDE-Q) at baseline, and 6 and 12 months post-surgery. Results: Patients experienced substantial weight loss and reported statistically significant reductions in BSQ, and Shape and Weight Concern scores from baseline to 6 and 12 months post-surgery. Improvements on the BSQ and Shape Concern scale were maintained between 6 and 12 months post-surgery, while patients reported continued reductions in weight and Weight Concern scale scores. Moreover, at 6 and 12 months follow-up, over 80% of female patients had body image scores comparable to published norms. Correlations between change in BMI and the body image measures were variable, and degree of weight loss did not predict body image scores 6 or 12 months post-surgery. Conclusions: Results from the present study illustrate significant and immediate post-surgical reductions in body dissatisfaction and concerns, along with weight loss in bariatric patients. Such improvements indicate a normalization of body image-related concerns in these patients, the majority of who remain overweight or obese despite the substantial post-surgical weight losses. Changes in weight and body image relate poorly to each other, suggesting that mediating factors may be involved.     

Type 2 Diabetes and Weight Loss following Biliopancreatic Diversion for Obesity

Background: The authors investigated the weight loss and maintenance in type 2 diabetic obese patients undergoing biliopancreatic diversion (BPD). Methods: Two series of diabetic and non-diabetic obese patients matched for gender, age and baseline body mass index (BMI) were evaluated prior to BPD, on the occasion of the regular follow-up visit at 1, 2 and 3 years following the operation, and at the fifth postoperative year. At each follow-up point, body weight (BW), BMI, and serum glucose concentration were measured. Results: In all type 2 diabetic patients, the serum glucose level fell to within the normal range at the first postoperative year and remained within normal limits without any medication throughout all the follow-up period. In preoperatively diabetic subjects, mean values of BW and BMI were closely similar to those of non-diabetic subjects at all follow-up points, and the stabilization weight was independently related to age and to initial BW values. Conclusions: In obese patients with type 2 diabetes, the glucose level steadily normalized in every case following BPD, and values remained unchanged throughout the follow-up period. After the operation, the type 2 diabetic obese patients experienced the same stable weight reduction as their non-diabetic counterparts.     

Ethnic Differences in Obesity and Surgical Weight Loss between African-American and Caucasian Females

Background: In the general population, African-American females are more obese and resistant to weight loss than Caucasian women. In the present study, we examined the severity of obesity among morbidly obese African-American and Caucasian females, studied the effectiveness of Roux-en-Y gastric bypass (RYGBP), and sought to identify factors contributing to obesity and weight loss. Methods: The study population included 153 morbidly obese females randomly selected from our general bariatric patient population. Anthropometric measurements consisted of body weight, body mass index (BMI), excess weight, and waist, hip, thigh, and neck circumferences. Factors that may contribute to obesity included age, age of obesity onset, number of childbirths, calorie intake, diet composition, and degree of psychological distress. The effects of RYBGP were studied in weight-matched groups of African-American and Caucasian females (n=37 per group) at weight loss nadir, i.e. 12 to 18 months after surgery. Results: We found that morbid obesity is more severe among African-American than Caucasian females. The greater degree of obesity of African-American, as compared to Caucasian, females is not due to ethnic differences in calorie intake, diet composition, age or age of obesity onset, number of childbirths, and psychological distress. RYGBP is less effective in reducing body fat and, consequently, excess body weight of the African-American than the Caucasian females, suggesting possible ethnic differences in fat metabolism. Conclusion: African-American females with morbid obesity have greater adiposity than do Caucasian women and lose significantly less body fat after RYGBP.     

Impact of Lactation on Maternal Body Weight and Body Composition

Women worldwide generally lose weight and bodyfat during lactation. This loss, although increased bylonger, more intensive breastfeeding, is modest and maybe reduced by increased food intake and decreased activity. Higher parity and older age areassociated with greater weight loss postpartum amongpoorly nourished women. Well-nourished women or thosewho breastfeed only for a limited time may not return to their prepregnant weight or body compositionby the end of the lactation period. Those who areoverweight or obese may have difficulty initiating ormaintaining lactation. For the majority of women in the world, lactation is unlikely to representa threat to their health. To advise women on how tooptimize their health and lactational performance, onemust consider all of the changes in maternal nutritional status that occur during a reproductive cycle,which may or may not compensate for the modest decreasesin body weight associated with lactation.     

Prevalence of Subclinical Hypothyroidism in a Morbidly Obese Population and Improvement after Weight Loss Induced by Roux-en-Y Gastric Bypass

Background:There are many studies concerning thyroid function in obesity, and some of them describe higher TSH levels in obese subjects. Few studies evaluated long-term changes in thyroid function caused by weight loss after bariatric surgery. Our aims were to evaluate the prevalence of subclinical hypothyroidism (SH) in a morbidly obese population and to analyze the effect of weight loss induced by Roux-en-Y gastric bypass (RYGBP) on TSH and thyroid hormone (TH) levels. Methods: TSH, free thyroxine (fT4) and total triiodothyronine (T3) levels were analyzed before and 12 months after RYGBP in patients with grade III or grade II obesity with co-morbidities. Subjects taking TH and/or with positive antithyroid antibodies and/or with overt hypothyroidism were excluded. Results: 72 subjects (62F/10M), with mean age 39.6±9.8 years and mean BMI 53.0±10.4 kg/m² were studied. The prevalence of SH before RYGBP was 25% (n=18). There was a significant post-surgical decrease in BMI in the whole population, as well as in SH patients. In the SH group and normal TSH group, there was a decrease in TSH and T3, but not in fT4. TSH was not correlated with initial BMI or percent change in BMI. TSH concentrations reached normal values in all SH patients after RYGBP. Conclusion: Our data confirm that severe obesity is associated with increased TSH. The decrease in TSH was independent of BMI, but occurred in all SH patients. A putative effect of weight reduction on the improvement of SH in all patients may be an additional benefit of bariatric surgery.     

Changes in Insulin Resistance Following Bariatric Surgery: Role of Caloric Restriction and Weight Loss

The prevalence of type 2 diabetes mellitus (T2DM) and obesity in the western world is steadily increasing. Bariatric surgery is an effective treatment of T2DM in obese patients. The mechanism by which weight loss surgery improves glucose metabolism and insulin resistance remains controversial. In this review, we propose that two mechanisms participate in the improvement of glucose metabolism and insulin resistance observed following weight loss and bariatric surgery: caloric restriction and weight loss. Nutrients modulate insulin secretion through the entero-insular axis. Fat mass participates in glucose metabolism through the release of adipocytokines. T2DM improves after restrictive and bypass procedures, and combinations of restrictive and bypass procedures in morbidly obese patients. Restrictive procedures decrease caloric and nutrient intake, decreasing the stimulation of the entero-insular axis. Gastric bypass (GBP) operations may also affect the entero-insular axis by diverting nutrients away from the proximal GI tract and delivering incompletely digested nutrients to the distal GI tract. GBP and biliopancreatic diversion combine both restrictive and bypass mechanisms. All procedures lead to weight loss and decrease in the fat mass. Decrease in fat mass significantly affects circulating levels of adipocytokines, which favorably impact insulin resistance. The data reviewed here suggest that all forms of weight loss surgery lead to caloric restriction, weight loss, decrease in fat mass and improvement in T2DM. This suggests that improvements in glucose metabolism and insulin resistance following bariatric surgery result in the short-term from decreased stimulation of the entero-insular axis by decreased caloric intake and in the long-term by decreased fat mass and resulting changes in release of adipocytokines. Observed changes in glucose metabolism and insulin resistance following bariatric surgery do not require the posit of novel regulatory mechanisms.