Effects of Roux-en-Y Gastric Bypass on Resting Energy Expenditure in Women

Weight loss maintenance after bariatric surgery

Metabolic and bariatric surgery (MBS) is an effective treatment for patients with morbid obesity and its comorbidities. However, many patients experience weight regain (WR) after achieving their nadir weight. Establishing the definition of WR is challenging as postoperative WR has various definitions. Risk factors for WR after MBS include anatomical, racial, hormonal, metabolic, behavioral, and psychological factors, and evaluating such factors preoperatively is necessary. Long-term regular follow-up and timely treatment by a multidisciplinary team are important because WR after surgery is multi-factorial. Although lifestyle interventions that focus on appropriate dietary education, physical activity education or interventions, and behavioral psychological interventions are suggested, more well-designed studies are needed because studies evaluating intervention methods and the effectiveness of WR prevention are lacking. Anti-obesity drugs can be used to prevent and manage patients with WR after MBS; however, more research is needed to determine the timing, duration, and type of anti-obesity drugs used to prevent WR.

Metabolic Slowing Vanished 5 Years After Sleeve Gastrectomy in Patients With Obesity and Prediabetes/Diabetes

BACKGROUND

Resting energy expenditure (REE) decreases after weight loss more than expected according to body composition changes. Metabolic adaptation (MA) or metabolic slowing represents the difference between measured (m) and predicted (p) REE, and it is not clear whether it persists in the long-term. The aim of this study is to evaluate MA occurring 1 year (V1) and 5 years (V5) after laparoscopic sleeve gastrectomy (LSG) in patients with obesity and normal glucose tolerance, prediabetes (preDM) and type 2 diabetes (T2DM).

METHODS

We reassessed 37 patients (14 males/23 females) of 44.8 ± 10 years old, since they registered all the biochemical, body composition, and REE assessments at baseline (V0), V1, and V5. Physical activity (PA) was assessed by interview and questionnaire.

RESULTS

Patients displayed a percentage of weight loss of 31.5 ± 7.4% at V1 and a weight regain of 8.9 ± 7.5% at V5. Comparing V1 and V5, fat mass showed a slight increase (P = 0.011), while free fat mass remained unchanged (P = 0.304). PA improved at V1 (P < 0.001), remaining stable at V5 (P = 0.9). Measured REE (mREE) displayed a 31.2% reduction with a corresponding decrease of predicted REE (pREE) of 21.4% at V1, compared with V0 (P = 0.005), confirming a significant MA at V1. Conversely, no difference between mREE and pREE was observed at V5 (P = 0.112).

CONCLUSION

Our results suggested that only patients with preDM and T2DM displayed MA at V1, which vanished 5 years after LSG. Patients who practiced more PA prevent MA after surgery-induced wight loss.

Sympathomimetic increases resting energy expenditure following bariatric surgery: A randomized controlled clinical trial

OBJECTIVE

The aim of this study was to test the hypothesis that ephedrine + caffeine (EC) reduces the fall in resting energy expenditure (REE) following bariatric surgery.

METHODS

This 32-week, randomized, double-blinded, placebo-controlled trial included 142 patients who underwent Roux-en-Y gastric bypass (RYGB) or sleeve gastrectomy (SG) surgery. Participants were randomized to either EC or placebo for 27 weeks, beginning 5 weeks post surgery. The primary end points were change in REE (measured), percentage of predicted REE ([measured REE/Harris-Benedict equation-predicted REE] × 100), and body composition. Secondary outcomes included change in percentage of weight. Adverse events (AEs) were recorded.

RESULTS

The reduction in REE was smaller in the EC versus the placebo group, but it was not significant. Percentage of predicted REE was increased in the EC versus the placebo group (difference, mean [SE]: 5.82 [2.29], p = 0.013). Percentage of weight (difference: -3.83 [1.39], p = 0.007) was reduced in the EC versus the placebo group. Percentage of predicted REE was increased and body weight decreased in the EC-treated participants who underwent SG compared with those who underwent SG and were treated with placebo (difference in percentage of predicted REE = 8.06 [2.83], p = 0.006; difference in weight percentage = -4.37 [1.92], p = 0.025). Percentage of fat-free mass was increased in the SG participants treated with EC versus placebo (difference: 1.31 [0.63], p = 0.042). The most common AEs were anxiety, dizziness, insomnia, and tremors. Most AEs were not different from placebo by Week 32.

CONCLUSIONS

EC enhances weight loss and reduces the fall in REE following bariatric surgery. Adrenergic symptoms mostly resolve over time.

The effect of additional protein on lean body mass preservation in post-bariatric surgery patients: a systematic review

BACKGROUND

As result of bariatric surgery, patients are susceptible to protein deficiency which can result in undesirable lean body mass (LBM) loss. Consumption of high-protein diets or supplements could counteract this, but evidence about the effect is scarce. This paper systematically reviewed the literature to determine the effect of additional protein intake (≥60 g/day) on LBM preservation in post-bariatric patients.

METHODS

An electronic search of PubMed, EMBASE and the Cochrane Library was conducted. Studies were included if patients received a high-protein diet or protein supplements for at least one month, and LBM was assessed. The primary outcome was difference in mean LBM loss between the experimental (protein) and control group. Secondary outcomes were differences in body fat mass, total body water, body mass index and resting metabolic rate.

RESULTS

Two of the five included studies (n = 223) showed that consumption of proteins resulted in significant LBM preservation. Only one study reported a significant difference in the reduction of body fat mass and resting metabolic rate in favour of a high-protein diet, but none of the studies showed a significant difference in total body water loss or body mass index change between the two groups.

CONCLUSIONS

This paper showed inconclusive evidence for LBM preservation due to protein supplementation or a high-protein diet in post-bariatric patients. This outcome might be subjected to certain limitations, including a lack of blinding and a low compliance rate reported in the included studies. More specific and personalized recommendations regarding protein intake may need to be established by high quality research. Studies investigating the quantity (g/day) and quality (whey, casein or soy) of proteins are also needed.

Thermic effect of food and resting energy expenditure after sleeve gastrectomy for weight loss in adolescent females

BACKGROUND

Few studies have addressed the effect of bariatric surgery on factors related to energy balance, including resting energy expenditure (REE) and thermic effect of food (TEF). To our knowledge, very few studies have examined changes in REE and none have investigated modifications in TEF after sleeve gastrectomy (SG) performed in adolescents.

OBJECTIVE

To assess energy expenditure in females who underwent SG as adolescents and matched-control participants as preliminary data about the potential of SG to confer differences in postprandial energy expenditure.

SETTING

Children's Hospital Medical Center, Cincinnati, Ohio, United States.

METHODS

In this observational study, REE and respiratory quotient (RQ) were measured via indirect calorimetry, followed by a standardized meal and assessment of TEF and postprandial RQ. Plasma drawn before and every 15 minutes after the meal was assayed for insulin, glucose, and C-peptide. Usual dietary intake was estimated using 24-hour recall interviews.

RESULTS

Fasting REE and RQ were similar between surgical and control groups. Postmeal TEF also did not differ between groups. The surgical group had higher RQ early in the postprandial period, whereas the control group RQ was higher after 125 minutes post meal. Compared with the control group, the surgical group had lower postprandial glucose, higher insulin and C-peptide, and consumed less daily energy during usual intake.

CONCLUSIONS

Postprandial RQ was consistent with the rapid gastric emptying typical of SG, yet we observed no group differences in REE or TEF. These findings may have been due to limited statistical power. More comprehensive studies of EE after SG are warranted.

Resting Energy Expenditure and Metabolic Adaptation in Adolescents at 12 Months After Bariatric Surgery

BACKGROUND

Evidence suggests that metabolic adaptation occurs after bariatric surgery such that resting energy expenditure (REE) declines more than accounted for by body weight or body composition changes in adults. Little is known about REE and metabolic adaptation among adolescents after bariatric surgery.

OBJECTIVE

To examine changes in REE and metabolic adaptation among adolescents at 12 months (12M) after bariatric surgery.

SETTING

Pediatric hospital, Canada.

METHODS

Adolescents undergoing Roux-en-Y gastric bypass (RYGB) or sleeve gastrectomy (SG) were followed. Bioelectrical impedance analysis and indirect calorimetry were completed to measure body composition and REE, respectively. Predicted REE was calculated using the Mifflin equation before and after bariatric surgery and a predictive equation using preoperative data.

RESULTS

Among 20 patients (15 girls), the mean age and body mass index at surgery were 17.2 ± 0.8 years and 48.7 ± 7.4 kg/m2, respectively. REE had decreased by 548.3 kcal/d at 12M postoperatively (P < 0.001). Metabolic adaptation, determined by two procedures, was negative and significantly different from baseline (P < 0.05). When stratified by surgery type, REE change at 12M was not significantly different (RYGB, -494.0 ± 260.9 kcal/d, n = 11; SG, -614.6 ± 344.4 kcal/d, n = 9; P = 0.384). Among 13 patients with REE data at 6 and 12M, no statistically significant difference was found (P = 0.368).

CONCLUSIONS

Predicted and measured REE was 19% and 25% lower at 12M, respectively, irrespective of bariatric surgery type. Metabolic adaptation might predispose adolescents to weight regain after bariatric surgery and warrants careful nutritional management and counseling.

Changes in Energy Expenditure of Patients with Obesity Following Bariatric Surgery: a Systematic Review of Prospective Studies and Meta-analysis

We herein summarize the available literature on the effects of bariatric surgery (BS) on energy expenditure in individuals with obesity. We conducted a systematic literature review, and 35 prospective studies met our inclusion criteria. The findings indicate that BS contributes to increased diet-induced thermogenesis (DIT) and decreased total energy expenditure (TEE) and resting energy expenditure (REE) in patients with obesity. The meta-analysis demonstrated a significant decrease in TEE and REE within 6 months following BS. With the sustained decrease in REE, there was no further decrease in TEE between the 6- and 12-month follow-up. Increased DIT might explain the variance between the patterns of REE and TEE change. The postoperative decrease in REE/FFM and increase in REE/BW were observed. The changes in substrate utilization might be consistent with the change in the respiration quotient postoperatively.

Nutritional and Micronutrient Care of Bariatric Surgery Patients: Current Evidence Update

PURPOSE OF REVIEW

The continued success of bariatric surgery to treat obesity and obesity-associated metabolic conditions creates a need for a strong understanding of clinical nutrition both before and after these procedures.

RECENT FINDINGS

Surgically induced alteration of gastrointestinal physiology can affect the nutrition of individuals, especially among those who have undergone malabsorptive procedures. While uncommon, a subset of patients may develop protein-calorie malnutrition. In these cases, nutrition support should be tailored to the severity of malnutrition. Among all patients who undergo bariatric surgery, high rates of micronutrient deficiencies have been observed. To mitigate these deficiencies, empiric supplementation with multivitamins, calcium citrate, and vitamin D is generally recommended. Periodic surveillance should be performed for commonly deficient micronutrients, including thiamin (B1), folate (B9), cobalamin (B12), iron, and vitamin D. Following Roux-en-Y gastric bypass, serum levels of copper and zinc should also be monitored. In addition, lipid-soluble vitamins should be monitored following biliopancreatic diversion with/without duodenal switch.

Energy Metabolic Adaptation and Cardiometabolic Improvements One Year After Gastric Bypass, Sleeve Gastrectomy, and Gastric Band

CONTEXT

It is not known whether the magnitude of metabolic adaptation, a greater than expected drop in energy expenditure, depends on the type of bariatric surgery and is associated with cardiometabolic improvements.

OBJECTIVE

To compare changes in energy expenditure (metabolic chamber) and circulating cardiometabolic markers 8 weeks and 1 year after Roux-en-y bypass (RYGB), sleeve gastrectomy (SG), laparoscopic adjustable gastric band (LAGB), or a low-calorie diet (LCD). Design, Setting, Participants, and Intervention: This was a parallel-arm, prospective observational study of 30 individuals (27 females; mean age, 46 ± 2 years; body mass index, 47.2 ± 1.5 kg/m²) either self-selecting bariatric surgery (five RYGB, nine SG, seven LAGB) or on a LCD (n = 9) intervention (800 kcal/d for 8 weeks, followed by weight maintenance).

RESULTS

After 1 year, the RYGB and SG groups had similar degrees of body weight loss (33-36%), whereas the LAGB and LCD groups had 16 and 4% weight loss, respectively. After adjusting for changes in body composition, 24-hour energy expenditure was significantly decreased in all treatment groups at 8 weeks (-254 to -82 kcal/d), a drop that only persisted in RYGB (-124 ± 42 kcal/d; P = .002) and SG (-155 ± 118 kcal/d; P = .02) groups at 1 year. The degree of metabolic adaptation (24-hour and sleeping energy expenditure) was not significantly different between the treatment groups at either time-point. Plasma high-density lipoprotein and total and high molecular weight adiponectin were increased, and triglycerides and high-sensitivity C-reactive protein levels were reduced 1 year after RYGB or SG.

CONCLUSIONS

Metabolic adaptation of approximately 150 kcal/d occurs after RYGB and SG surgery. Future studies are required to examine whether these effects remain beyond 1 year.

Energy Adaptations Persist 2 Years After Sleeve Gastrectomy and Gastric Bypass

Non-surgical weight loss induces a greater than expected decrease in energy expenditure, a phenomenon known as 'metabolic adaptation'. The effects of different bariatric surgery procedures on metabolic adaptation are not yet known and may partially contribute to weight loss success. We compared resting energy expenditure (REE) in 35 subjects (nine males; age = 46 ± 11 years; BMI = 42.1 ± 6.5 kg/m(2)) undergoing gastric band, sleeve gastrectomy or Roux-en-Y gastric bypass (RYGB) up to 2 years after surgery. We found a greater than expected reduction of 130-300 kcal/day at 6 weeks after sleeve and bypass surgery which was not explained by changes in body composition; this change was not seen in the band group. The suppression in REE after sleeve and RYGB remained up to 2 years, even after weight loss had plateaued. Our findings suggest that energy adaptation is not a contributing mechanism to medium-term weight maintenance after sleeve and RYGB bariatric surgeries.

UCP1 and UCP3 Expression Is Associated with Lipid and Carbohydrate Oxidation and Body Composition

BACKGROUND/OBJECTIVE

Uncoupling proteins (UCPs) are located in the inner membrane of mitochondria. These proteins participate in thermogenesis and energy expenditure. This study aimed to evaluate how UCP1 and UCP3 expression influences substrate oxidation and elicits possible changes in body composition in patients submitted to bariatric surgery.

SUBJECTS/METHODS

This is a longitudinal study comprising 13 women with obesity grade III that underwent bariatric surgery and 10 healthy weight individuals (control group). Body composition was assessed by bioelectrical impedance. Carbohydrate and fat oxidation was determined by indirect calorimetry. Subcutaneous adipose tissue was collected for gene expression analysis. QPCR was used to evaluate UCP1 and UCP3 expression.

RESULTS

Obese patients and the control group differed significantly in terms of lipid and carbohydrate oxidation. Six months after bariatric surgery, the differences disappeared. Lipid oxidation correlated with the percentage of fat mass in the postoperative period. Multiple linear regression analysis showed that the UCP1 and UCP3 genes contributed to lipid and carbohydrate oxidation. Additionally, UCP3 expression was associated with BMI, percentage of lean body mass, and percentage of mass in the postoperative period.

CONCLUSIONS

UCP1 and UCP3 expression is associated with lipid and carbohydrate oxidation in patients submitted to bariatric surgery. In addition, UCP3 participates in body composition modulation six months postoperatively.

Mechanism Underlying the Weight Loss and Complications of Roux-en-Y Gastric Bypass. Review

Various bariatric surgical procedures are effective at improving health in patients with obesity associated co-morbidities, but the aim of this review is to specifically describe the mechanisms through which Roux-en-Y gastric bypass (RYGB) surgery enables weight loss for obese patients using observations from both human and animal studies. Perhaps most but not all clinicians would agree that the beneficial effects outweigh the harm of RYGB; however, the mechanisms for both the beneficial and deleterious (for example postprandial hypoglycaemia, vitamin deficiency and bone loss) effects are ill understood. The exaggerated release of the satiety gut hormones, such as GLP-1 and PYY, with their central and peripheral effects on food intake has given new insight into the physiological changes that happen after surgery. The initial enthusiasm after the discovery of the role of the gut hormones following RYGB may need to be tempered as the magnitude of the effects of these hormonal responses on weight loss may have been overestimated. The physiological changes after RYGB are unlikely to be due to a single hormone, or single mechanism, but most likely involve complex gut-brain signalling. Understanding the mechanisms involved with the beneficial and deleterious effects of RYGB will speed up the development of effective, cheaper and safer surgical and non-surgical treatments for obesity.

[Surgery as pluripotent instrument for metabolic disease. What are the mechanisms?]

Bariatric metabolic surgery currently offers the most effective treatment to achieve sustained weight loss and improvement in metabolic comorbidities, such as type 2 diabetes, hypertension, dyslipidemia and cardiovascular diseases. The number of cases performed in Germany and also worldwide is continuously increasing but the underlying mechanisms of bariatric metabolic surgery are still not completely elucidated. Roux-en-Y gastric bypass (RYGB) surgery represents one of the most commonly used and therefore most frequently investigated bariatric metabolic procedures. Traditionally, its effectiveness was attributed to food restriction and malabsorption but in the meantime it has become evident that the underlying postoperative mechanisms of RYGB seem to be much more complex. Potential mechanisms include multiple physiological changes, such as altered levels of gastrointestinal hormones, increased energy expenditure and modified gut microbiota as well as many other factors. This review article therefore aims to offer an up to date overview of relevant mechanisms that improve obesity and its associated comorbidities after RYGB surgery.

Laparoscopic sleeve gastrectomy and Roux-en-Y gastric bypass lead to equal changes in body composition and energy metabolism 17 months postoperatively: a prospective randomized trial

BACKGROUND

Weight loss is the sum of fat and lean mass loss. The aim of this study was to examine whether there are differences between 2 surgical procedures, laparoscopic sleeve gastrectomy (LSG) and laparoscopic Roux-en-Y gastric bypass (LRYGB), in terms of their effect on body composition and energy metabolism. In addition, the predictive value of preoperative body composition and energy metabolism on postoperative outcome was evaluated.

SETTING

All procedures were performed by the same surgeon (RP) at the St. Claraspital Basel in Switzerland. Calorimetry and DEXA were carried out at the same institution (Interdisciplinary Center of Nutritional and Metabolic Diseases, St. Claraspital Basel).

METHODS

Forty-two morbidly obese, mainly female (85%), nondiabetic and diabetic (50%) patients (body mass index [BMI]: 43.9 kg/m(2)±1.3) before and 17±5.6 months after LSG (n = 23) and LRYGB (n = 19) were examined. Body composition was analyzed by dual-energy X-ray absorptiometry (DEXA) and resting energy expenditure (REE); fat and carbohydrate oxidation was determined by indirect calorimetry.

RESULTS

Follow-up was 100%. Excessive BMI loss (EBMIL) was 64.4% in the LSG group and 76.4% in the LRYGB group (P<.046). In both groups total fat and muscle mass decreased significantly compared with baseline (P<.001) and the percentage of muscle mass per kilogram of weight increased postoperatively (results not significant). REE decreased (P<.001) and REE per kilogram of weight increased significantly (P<.003) compared with baseline. Carbohydrate oxidation remained stable in both groups, and fat oxidation decreased significantly (P<.001) compared with baseline. In diabetic patients compared with nondiabetic patients there were no statistically significant differences in REE, substrate oxidation, or reduction in truncal fat. Postoperatively, lean mass was higher in diabetic patients (P = .037). Preoperative indirect calorimetry and DEXA results were of no predictive value for outcome.

CONCLUSION

Changes in REE and body composition were equal after both procedures in a bariatric population mainly consisting of women. No predictors for amount of weight loss could be found.

Roux-en-Y Gastric Bypass Surgery Increases Respiratory Quotient and Energy Expenditure during Food Intake

Objective

The mechanisms determining long-term weight maintenance after Roux-en-Y gastric bypass (RYGB) remain unclear. Cross sectional studies have suggested that enhanced energy expenditure (EE) may play a significant role and the aim of this study was to reveal the impact of RYGB on each major component constituting total EE.

Design

Six obese female subjects, without other co-morbidities, were assessed before and at 10 days, 3 and 20 months after RYGB. Indirect calorimetry in a metabolic chamber was used to assess 24h EE at each study visit. Other measurements included body composition by DEXA, gut hormone profiles and physical activity (PA) using high sensitivity accelerometers.

Results

Median Body Mass Index decreased from 41.1 (range 39.1-44.8) at baseline to 28 kg/m² (range 22.3-30.3) after 20 months (p<0.05). Lean tissue decreased from 55.9 (range 47.5-59.3) to 49.5 (range 41.1-54.9) kg and adipose tissue from 61 (range 56-64.6) to 27 (range 12-34.3) kg (both p<0.05). PA over 24h did not change after surgery whereas 24h EE and basal metabolic rate (BMR) decreased. EE after a standard meal increased after surgery when adjusted for total tissue (p<0.05). After an initial drop, RQ (respiratory quotient) had increased at 20 months, both as measured during 24h and after food intake (p<0.05).

Conclusion

RYGB surgery up-regulates RQ and EE after food intake resulting in an increased contribution to total EE over 24h when corrected for total tissue.

The physiology underlying Roux-en-Y gastric bypass: a status report

Obesity and its related comorbidities can be detrimental for the affected individual and challenge public health systems worldwide. Currently, the only available treatment options leading to clinically significant and maintained body weight loss and reduction in obesity-related morbidity and mortality are based on surgical interventions. This review will focus on two main clinical effects of Roux-en-Y gastric bypass (RYGB), namely body weight loss and change in eating behavior. Animal experiments designed to understand the underlying physiological mechanisms of these post-gastric bypass effects will be discussed. Where appropriate, reference will also be made to vertical sleeve gastrectomy. While caloric malabsorption and mechanical restriction seem not to be major factors in this respect, alterations in gut hormone levels are invariably found after RYGB. However, their causal role in RYGB effects on eating and body weight has recently been challenged. Other potential factors contributing to the RYGB effects include increased bile acid concentrations and an altered composition of gut microbiota. RYGB is further associated with remarkable changes in preference for different dietary components, such as a decrease in the preference for high fat or sugar. It needs to be noted, however, that in many cases, the question about the necessity of these alterations for the success of bariatric surgery procedures remains unanswered.

AGE AND GENDER MAY INFLUENCE THE RESULTS OF ROUX-EN-Y GASTRIC BYPASS? Metabolic syndrome parameters

Context Severe obesity affects the body favoring the development of serious diseases, including hypertension, diabetes mellitus, atherosclerosis and non alcoholic fatty liver disease. Bariatric procedures increased in Brazil in the last decade. Objectives The purpose of this study was to verify if gender and age in date of procedure resulted significant differences in metabolic syndrome parameters after surgery. Methods The study involved 205 medical records of adult patients undergoing Roux-en-Y gastric bypass, stratified by gender and age groups and followed one year by a multidisciplinary team. Results It was observed significant decrease in body mass index, fasting glucose and insulin at all ages and both genders. Lipid profile showed significant improvements except high density lipoprotein cholesterol. Ectopic fat in the liver has decreased after 6 months in patients classified with steatosis at baseline. Patients classified as hypertensive blood pressure levels decreased 6 months after surgical intervention. Conclusions Roux-en-Y gastric bypass proved to be an important tool in remission of metabolic syndrome parameters. The reduction of body mass accompanied to decrease in insulin resistance resulted in lower prevalence of comorbidities associated with obesity. The benefits were similar and extended both genders and all age groups between 18 and 65 years old.

Physiological mechanisms behind Roux-en-Y gastric bypass surgery

Obesity and its related comorbidities can be detrimental for the affected individual and challenge public health systems worldwide. Currently, the only available treatment options leading to clinically significant and maintained body weight loss and reduction in obesity-related morbidity and mortality are based on surgical interventions. Apart from the 'gold standard' Roux-en-Y gastric bypass (RYGB), the vertical sleeve gastrectomy and gastric banding are two frequently performed procedures. This review will discuss animal experiments designed to understand the underlying mechanisms of body weight loss after bariatric surgery. While caloric malabsorption and mechanical restriction are no major factors in this respect, alterations in gut hormone levels are invariably found after RYGB. However, their causal role in RYGB effects on eating and body weight has recently been challenged. Other potential factors contributing to the RYGB effects include increased bile acid concentrations and an altered composition of gut microbiota. RYGB is further associated with remarkable changes in the preference for different dietary components such as a decrease in the preference for high fat or sugar; it is important to note that the contribution of altered food preferences to the RYGB effects on body weight is not clear.

Predicted vs. Actual Resting Energy Expenditure and Activity Coefficients: Post-Gastric Bypass, Lean and Obese Women

Total Energy Expenditure (TEE) and energy requirements are commonly estimated from equations predicting Resting Energy Expenditure (REE) multiplied by a Physical Activity (PA) coefficient that accounts for both PA energy expenditure and the thermogenic effect of food. PA coefficients based on PA self-reports are a potential source of error that has not been evaluated. Therefore, in this study we compared: 1) the Harris-Benedict (HB), Mifflin-St. Jeor (MSJ), and the Food and Agriculture Organization/World Health Organization/United Nations University (FAO/WHO/UNU) REE equations with REE measured (REE-m) with indirect calorimetry; 2) PA coefficients determined with PA self-reports vs. objectively assessed PA; and 3) TEE estimates in post-Gastric Bypass (GB = 13), lean (LE = 7), and obese (OB = 12) women. REE was measured in the morning after an overnight fast with participants resting supine for 30 min. Self-reported PA was evaluated with a questionnaire and objectively measured with accelerometers worn for 5-7 days. Nutritional intake was evaluated with a food frequency questionnaire. Anthropometry included DEXA, and abdominal CT scans. Eligible GB had surgery ≥ 12 months before the study, and had ≥ 10 kg of body weight loss. All participants were 18-45 years of age, able to engage in ambulatory activities, and not taking part in exercise training programs. One-way ANOVA was used to detect differences in REE and TEE. Accuracy of REE prediction equations were determined by cases within 10% of REE-m, and agreement analyses. REE predictions were not different than REE-m, but agreements were better with HB and MSJ, particularly in the GB and LE groups. Discrepancies in the PA coefficients determined with self-report vs. objectively assessed PA resulted in TEE overestimates (approximately 200-300 Kcal/day) using HB and MSJ equations. FAO/WHO/UNU overestimated TEE in all groups regardless of the PA assessment method (approximately 300-900 kcal/day). These results suggest that: 1) HB and MSJ equations are good predictors of REE among GB and LE, but not among OB women, 2) PA coefficients used to estimate TEE must be determined with objective PA assessment, and 3) TEE estimates using PA coefficients with the FAO/WHO/UNU equation must be used with caution.

Bile acids and gut peptide secretion after bariatric surgery: a 1-year prospective randomized pilot trial

OBJECTIVE

Increased delivery of bile acid salts (BA) to distal L-cells and altered TGR5 receptor activation may contribute to the early and substantial increases in gut peptide secretion seen after bariatric surgery. To further elucidate a potential role of BA in the secretion of GLP-1 and PYY, we analyzed plasma BA concentrations in 14 morbidly obese patients undergoing gastric bypass or sleeve gastrectomy in a prospective, randomized 1-year trial.

DESIGN AND METHODS

Patients received a standard test meal and blood was collected before and after eating, prior to, and 1 week, 3 months, and 12 months after surgery.

RESULTS

Pre-surgery, basal BA concentrations were significantly lower in bariatric patients than in healthy controls. One year post-surgery, bariatric patients expressed variably increased BA concentrations (gastric bypass patients ∼2 fold increase, P ≤ 0.05). However, whereas in both patient groups, marked increases in GLP-1 and PYY and improved glycemic control was seen already 1 week and 3 months post-surgery, changes in plasma BA followed a different pattern: basal and postprandial plasma BA concentrations increased much slower, more progressively with significant increases only 1-year post-surgery.

CONCLUSIONS

Based on these findings, BA do not appear to be key mediators of the early increase in GLP-1 and PYY response in post-bariatric patients.

Longitudinal assessment of food intake, fecal energy loss, and energy expenditure after Roux-en-Y gastric bypass surgery in high-fat-fed obese rats

BACKGROUND

The efficacy of Roux-en-Y gastric bypass (RYGB) surgery to produce weight loss has been well-documented, but few studies have measured the key components of energy balance, food intake, and energy expenditure longitudinally.

METHODS

Male Sprague-Dawley rats on a high-fat diet underwent either RYGB, sham operation, or pair feeding and were compared to chow-fed lean controls. Body weight and composition, food intake and preference, energy expenditure, fecal output, and gastric emptying were monitored before and up to 4 months after intervention.

RESULTS

Despite the recovery of initially decreased food intake to levels slightly higher than before surgery and comparable to sham-operated rats after about 1 month, RYGB rats maintained a lower level of body weight and fat mass for 4 months that was not different from chow-fed age-matched controls. Energy expenditure corrected for lean body mass at 1 and 4 months after RYGB was not different from presurgical levels and from all other groups. Fecal energy loss was significantly increased at 6 and 16 weeks after RYGB compared to sham operation, and there was a progressive decrease in fat preference after RYGB.

CONCLUSIONS

In this rat model of RYGB, sustained weight loss is achieved by a combination of initial hypophagia and sustained increases in fecal energy loss, without change in energy expenditure per lean mass. A shift away from high-fat towards low-fat/high-carbohydrate food preference occurring in parallel suggests long-term adaptive mechanisms related to fat absorption.

Effects of RYGB on energy expenditure, appetite and glycaemic control: a randomized controlled clinical trial

OBJECTIVES

Increased energy expenditure (EE) has been proposed as an important mechanism for weight loss following Roux-en-Y gastric bypass (RYGB). However, this has never been investigated in a controlled setting independent of changes in energy balance. Similarly, only few studies have investigated the effect of RYGB on glycaemic control per se. Here, we investigated the effect of RYGB on EE, appetite, glycaemic control and specific signalling molecules compared with a control group in comparable negative energy balance.

SUBJECTS/METHODS

Obese normal glucose-tolerant participants were randomized to receive RYGB after 8 (n=14) or 12 weeks (n=14). The protocol included a visit at week 0 and three visits (weeks 7, 11 and 78) where 24-h EE, appetite and blood parameters were assessed. Participants followed a low-calorie diet from weeks 0-11, with those operated at week 12 serving as a control group for those operated at week 8.

RESULTS

Compared with controls, RYGB-operated participants had lower body composition-adjusted 24-h EE and basal EE 3 weeks postoperatively (both P<0.05) but EE parameters at week 78 were not different from preoperative values (week 7). Surgery changed the postprandial response of glucagon-like peptide-1 (GLP-1), peptide YY3-36 (PYY), ghrelin, cholecystokinin, fibroblast growth factor-19 and bile acids (all P<0.05). Particularly, increases in GLP-1, PYY and decreases in ghrelin were associated with decreased appetite. None of HOMA-IR (homeostasis model assessment-estimated insulin resistance), Matsuda index, the insulinogenic index, the disposition index and fasting hepatic insulin clearance were different between the groups, but RYGB operated had lower fasting glucose (P<0.05) and the postprandial glucose profile was shifted to the left (P<0.01).

CONCLUSIONS

Our data do not support that EE is increased after RYGB. More likely, RYGB promotes weight loss by reducing appetite, partly mediated by changes in gastrointestinal hormone secretion. Furthermore, we found that the early changes in glycaemic control after RYGB is to a large extent mediated by caloric restriction.

Surgical weight loss: impact on energy expenditure

Diet-induced weight loss is often limited in its magnitude and often of short duration, followed by weight regain. On the contrary, bariatric surgery now commonly used in the treatment of severe obesity favors large and sustained weight loss, with resolution or improvement of most obesity-associated comorbidities. The mechanisms of sustained weight loss are not well understood. Whether changes in the various components of energy expenditure favor weight maintenance after bariatric surgery is unclear. While the impact of diet-induced weight loss on energy expenditure has been widely studied and reviewed, the impact of bariatric surgery on total energy expenditure, resting energy expenditure, and diet-induced thermogenesis remains unclear. Here, we review data on energy expenditure after bariatric surgery from animal and human studies. Bariatric surgery results in decreased total energy expenditure, mainly due to reduced resting energy expenditure and explained by a decreased in both fat-free mass and fat mass. Limited data suggest increased diet-induced thermogenesis after gastric bypass, a surgery that results in gut anatomical changes and modified the digestion processes. Physical activity and sustained intakes of dietary protein may be the best strategies available to increase non-resting and then total energy expenditure, as well as to prevent the decline in lean mass and resting energy expenditure.

Increased postprandial energy expenditure may explain superior long term weight loss after Roux-en-Y gastric bypass compared to vertical banded gastroplasty

Background and Aims

Gastric bypass results in greater weight loss than Vertical banded gastroplasty (VBG), but the underlying mechanisms remain unclear. In addition to effects on energy intake the two bariatric techniques may differentially influence energy expenditure (EE). Gastric bypass in rats increases postprandial EE enough to result in elevated EE over 24 hours. This study aimed to investigate alterations in postprandial EE after gastric bypass and VBG in humans.

Methods

Fourteen women from a randomized clinical trial between gastric bypass (n = 7) and VBG (n = 7) were included. Nine years postoperatively and at weight stability patients were assessed for body composition and calorie intake. EE was measured using indirect calorimetry in a respiratory chamber over 24 hours and focused on the periods surrounding meals and sleep. Blood samples were analysed for postprandial gut hormone responses.

Results

Groups did not differ regarding body composition or food intake either preoperatively or at study visit. Gastric bypass patients had higher EE postprandially (p = 0.018) and over 24 hours (p = 0.048) compared to VBG patients. Postprandial peptide YY (PYY) and glucagon like peptide 1 (GLP-1) levels were higher after gastric bypass (both p<0.001).

Conclusions

Gastric bypass patients have greater meal induced EE and total 24 hours EE compared to VBG patients when assessed 9 years postoperatively. Postprandial satiety gut hormone responses were exaggerated after gastric bypass compared to VBG. Long-term weight loss maintenance may require significant changes in several physiological mechanisms which will be important to understand if non-surgical approaches are to mimic the effects of bariatric surgery.

Energy expenditure before and after Roux-en-Y gastric bypass

BACKGROUND

Weight loss may decrease the energy expenditure (EE) because of changes in body composition (BC). The reduction in EE may contribute, in part, to weight regain. Experimental studies in animals indicate that Roux-en-Y Gastric Bypass (RYGB) increases the resting metabolic rate (RMR) when adjusted for body weight (BW). Thus, the aim of this study was to assess the clinical effects of RYGB on EE in patients who have undergone RYGB.

METHODS

The study was prospective and included 46 RYGB patients whose RMR was assessed prior to and at least 6 months post-surgery by indirect calorimetry. BW and BC were measured at these same time points using bioelectric impedance. RMR was adjusted for changes in BW, i.e., kilocalories per kilogram. Statistical tests were used to analyze the results.

RESULTS

The BW-adjusted RMR (kilocalories per kilogram) increased post-RYGB by 17.66 % (p < 0.0001). RMR adjusted for BW was negatively correlated to the total percentage of body fat preoperatively (r = -0.30729, p = 0.0378) and postoperatively (r = -0.46731, p = 0.0011) and was positively correlated to the fat-free mass percentage (%FFM) both preoperatively and postoperatively. Furthermore, BW-adjusted RMR and %FFM were positively correlated to percent excess weight loss (r = 0.55398, p < 0.0001 and r = 0.31677, p = 0.0283, respectively).

CONCLUSIONS

Weight loss following RYGB is associated with an increase in BW-adjusted RMR and with %FFM. An increase in energy expenditure post-RYGB may be responsible, in part, for successful long-term weight loss of the RYGB procedure.

Conjugated bile acids associate with altered rates of glucose and lipid oxidation after Roux-en-Y gastric bypass

BACKGROUND

Laparoscopic Roux-en-Y gastric bypass (RYGB) induces a more favorable metabolic profile than expected by weight loss alone. In this study, we investigated the effect of RYGB on serum bile acid levels and their relation to clinical outcomes.

METHODS

We included 30 obese patients who underwent RYGB (BMI = 46.1 ± 5.9 kg/m(2)). Clinical measurements and laboratory determinations were performed before surgery and 1 year after surgery. Fasting serum bile acids were measured by an enzymatic method and individual bile acids were quantified by HLPC-tandem mass spectrometry. Indirect calorimetry was performed to measure the rates of energy expenditure and substrate oxidation.

RESULTS

Fasting total serum bile acid levels increased twofold after RYGB (pre, 3.68 ± 2.03 vs. post, 7.06 ± 9.65 μmol/l, +92 %, p = 0.002). This increase in total bile acids was accompanied by a decrease in conjugated bile acids, which correlated with decreased glucose oxidation (r = 0.571, p = 0.002) and with increased lipid oxidation (r = -0.626, p = 0.0004). The change in taurine-conjugated bile acids correlated with altered DIO2 mRNA expression in adipose tissue (r = -0.498, p = 0.013) potentially linking bile acid conjugation to substrate oxidation through DIO2.

CONCLUSIONS

Fasting serum bile acid levels increase after RYGB. More specifically, changes in bile acid conjugation after RYGB associate with altered energy metabolism.

Resting energy expenditure of morbidly obese patients using indirect calorimetry: a systematic review

The increasing proportion of acutely ill hospital patient admissions presenting with a morbidly obese body mass index (BMI ≥ 40 kg m(-2) ) as a comorbidity is an emerging clinical concern. Suboptimal food intake and malnutrition is prevalent in the acute care hospital setting. The energy requirements necessary to prevent malnutrition in acutely ill patients with morbid obesity remains unclear. The aim of this systematic review was to identify studies in the literature that have used indirect calorimetry to measure the resting energy expenditure of patients with morbid obesity to establish their minimum energy requirements and the implications for optimal feeding practices in acutely ill hospitalized patients. A total of 20 studies from PubMed, Cochrane Library and Embase met the inclusion criteria and were reviewed. All articles were graded using the Australian National Health and Medical Research Council levels of evidence and given a quality rating using the American Dietetic Association recommendations. Studies were categorized according to the mean BMI of its subjects. The most commonly measured resting energy expenditures for morbidly obese patients are between 2,000 and 3,000 kcal d(-1) (8,400-12,600 kJ d(-1) ). Activity and injury factors of acutely ill morbidly obese patients could result in significantly greater energy requirements for this patient group and are unlikely to be met by standard hospital menus. Establishing the minimum energy requirements for this population group will help inform adequate and accurate energy provision in the acute setting. Outcomes of underfeeding and overfeeding in morbidly obese patients warrant further research.

Resting energy expenditure and energetic cost of feeding are augmented after Roux-en-Y gastric bypass in obese mice

Although the prevalence of obesity has increased dramatically throughout the world during the last 25 yr, its long-term control remains poor. Currently, only gastrointestinal weight loss surgery, especially Roux-en-Y gastric bypass (RYGB), is associated with substantial and sustained weight loss and resolution or significant improvement of diabetes mellitus and other metabolic obesity-induced complications. Clinical observations and recent studies have suggested that RYGB induces its effects by changing the physiology of weight regulation. Understanding the underlying mechanisms of these profound and sustainable effects could facilitate the development of novel and less invasive treatments against obesity and its complications. To study the physiological mechanisms of RYGB, we have developed a mouse RYGB model that replicates the human operation. The aims of this study were to develop a roadmap for assessing energy expenditure (EE) in animal models of weight loss surgery and to examine the effects of RYGB on EE. We first measured EE by indirect calorimetry in groups of animals that underwent RYGB or a sham operation. Calorimetry data were analyzed using three different methods: normalization by total body mass, allometric scaling, and analysis of covariance modeling. RYGB in mice induced a significant increase in EE that was independent of the method used. An energy balance analysis was then performed, which also confirmed that RYGB-treated animals have higher energy maintenance needs. Finally, we determined the EE components that account for the observed increase in EE, and we found that resting EE and postprandial thermogenesis are the major contributors to this increase.

Hypocaloric home parenteral nutrition and nutrition parameters in patients following bariatric surgery

BACKGROUND

Surgical intervention is considered an acceptable treatment for morbid obesity. Complications following bariatric surgery procedures (BSPs) may necessitate home parenteral nutrition (HPN). No studies have been published on patients receiving HPN following BSP complications. The study aim was to determine if hypocaloric HPN has an effect on body mass index (BMI), albumin, and HPN complications.

METHODS

A historic cohort of patients was identified from a clinical database. Obese patients (BMI ≥35 kg/m(2)) who underwent BSP and received HPN for an anastomotic leak/fistula or bowel obstruction were included. Comparisons for start and end of therapy were made for calorie and protein intake, BMI, white blood cell count, and serum albumin level. Readmissions and metabolic and infectious complications were recorded. Obese patients received hypocaloric feeds to promote weight loss and protein for wound healing.

RESULTS

Twenty-three patients were included for an average study length of 1.5 months. Patients received an average of 1.2 g of protein and a median of 13.6 kcal per kg actual body weight (ABW) per day. BMI decreased by 7.1% ± 5.2%, from a median of 39.8 to 37.1, and serum albumin increased by 12.5%, from 2.8 ± 0.5 to 3.2 ± 0.6 g/dL. Readmissions occurred in 52.2% of patients with 40.0% of complications related to HPN.

CONCLUSIONS

Hypocaloric HPN is efficacious in maintaining adequate nutrition while allowing for weight loss in morbidly obese patients following complications of bariatric surgery. Frequency of HPN complications was comparable to those reported in the literature.

Probing the mechanisms of the metabolic effects of weight loss surgery in humans using a novel mouse model system

BACKGROUND

Gastrointestinal weight loss surgery, especially Roux-en-Y gastric bypass (RYGB), is the most effective treatment for severe obesity. RYGB is associated with a remarkable decrease in the rate of death from obesity-related complications, such as diabetes mellitus, coronary artery disease, and cancer. Dissecting the mechanisms of RYGB effects could augment our understanding about the pathogenesis of obesity and its complications.

OBJECTIVES AND METHODS

In this study, we describe in detail a mouse model of RYGB that closely reproduces the surgical steps of the human procedure.

RESULTS

We show that RYGB in mice has the same effects as in human patients, proving the high translational validity of this model system. We present an intraoperative video to facilitate the widespread use of this complex and difficult method.

CONCLUSIONS

The study of the mechanisms of RYGB using this model system can greatly facilitate our understanding about the effects of RYGB in human patients. The reverse engineering of the physiological mechanisms of RYGB could lead to discovery of new, effective, and less invasive treatments.

Gastrointestinal hormones, energy balance and bariatric surgery

Despite increasing understanding of the changes in gastrointestinal and central neuroendocrine signaling following gastric bypass surgery (GBP) in morbidly obese patients, the mechanisms underlying weight loss and weight loss maintenance are not completely understood. Changes in energy expenditure are increasingly recognized as an important factor contributing to weight loss and metabolic effects in patients following GBP surgery. Experimental data regarding changes in energy balance following metabolic surgery in animal models suggest increased energy expenditure postoperatively as an important factor in the process of weight loss. However, the underlying neuroendocrine mechanisms are not well understood, and data regarding changes in energy expenditure in humans after GBP are inconsistent because of heterogenic patient populations and variable techniques. Nevertheless, a growing body of knowledge and understanding of the complex entero-neurohumoral interaction with its consequences in appetite, satiety and energy expenditure will help reveal the mechanisms of weight loss and weight loss maintenance following GBP surgery. Here we review how gastrointestinal hormones potentially regulate energy balance, and summarize current available experimental and clinical data on energy expenditure following obesity surgery.

Obesity surgery and gut-brain communication

The prevalence of obesity, and the cluster of serious metabolic diseases it is associated with, continues to rise globally, and hopes for effective treatment with drugs have been considerably set back. Thus, success with bariatric surgeries to induce sustained body weight loss and effectively cure most of the associated co-morbidities appears almost "miraculous" and systematic investigation of the mechanisms at work has gained momentum. Here, we will discuss the basic organization of gut-brain communication and review clinical and pre-clinical investigations on the potential mechanisms by which gastric bypass surgery leads to its beneficial effects on energy balance and glucose homeostasis. Although a lot has been learned regarding changes in energy intake and expenditure, secretion of gut hormones, and improvement in glucose homeostasis, there has not yet been the "breakthrough observation" of identifying a key signaling component common to the beneficial effects of the surgery. However, given the complexity and redundancy of gut-brain signaling and gut signaling to other relevant organs, it is perhaps more realistic to expect a number of key signaling changes that act in concert to bring about the "miracle".

Nutritional effect of oral supplement enriched in beta-hydroxy-beta-methylbutyrate, glutamine and arginine on resting metabolic rate after laparoscopic gastric bypass

BACKGROUND

Weight regain that begins 12-18 months after laparoscopic gastric bypass has been attributed to changes in resting metabolic rate (RMR), which is largely determined by lean body mass (LBM). An oral supplement containing beta-hydroxy-beta-methylbutyrate, glutamine, and arginine (HMB/Glu/Arg) has helped to restore LBM in cachexia due to cancer and in critically ill trauma patients. The objective of this study was to evaluate the effect of oral HMB/Glu/Arg on LBM and RMR following laparoscopic gastric bypass (LGB).

METHODS

Patients who underwent LGB were randomized to receive 24 g of HMB/Glu/Arg dissolved in water twice daily for 8 weeks or to receive no supplement. Weight loss, LBM, and RMR were assessed preoperatively, 2 and 8 weeks postoperatively. LBM was determined by dual emission x-ray absorptiometry (DXA) and RMR was measured by indirect calorimetry.

RESULTS

Thirty patients were enrolled: 80% white; 20% African American; 96.7% women; mean age 46.9±8.4 years; mean weight 113.4±11.6 kg; and mean body mass index (BMI) 43.3±4.1 kg/m2. The experimental and control groups included 14 and 16 patients, respectively, and there was no difference in baseline demographics and characteristics between the two groups. At 8 weeks, weight, BMI, LBM, and RMR significantly decreased by 15.7±2.5 kg, 6.0±1.0 kg/m2, 7.8±4.0 kg, and 290.6±234.9 kcal/day, respectively (P<0.0001 for each variable). However, when comparing these changes between the two groups, no statistical significance was observed.

CONCLUSIONS

There is a significant decrease in weight, BMI, LBM, and RMR in all subjects after LGB, and these changes were not affected by the use of HMB/Glu/Arg. Potential preservation of LBM as a result of HMB/Glu/Arg requires further investigation. However, its consumption (78 calories per serving) did not adversely affect weight loss in the experimental group.

Plasma bile acids are not associated with energy metabolism in humans

Bile acids (BA) have recently been shown to increase energy expenditure in mice, but this concept has not been tested in humans. Therefore, we investigated the relationship between plasma BA levels and energy expenditure in humans. Type 2 diabetic (T2DM) patients (n = 12) and gender, age and BMI-matched healthy controls (n = 12) were studied before and after 8 weeks of treatment with a BA sequestrant. In addition, patients with liver cirrhosis (n = 46) were investigated, since these display elevated plasma BA together with increased energy expenditure. This group was compared to gender-, age- and BMI-matched healthy controls (n = 20). Fasting plasma levels of total BA and individual BA species as well as resting energy expenditure were determined. In response to treatment with the BA sequestrant, plasma deoxycholic acid (DCA) levels decreased in controls (-60%, p < 0.05) and T2DM (-32%, p < 0.05), while chenodeoxycholic acid (CDCA) decreased in controls only (-33%, p < 0.05). Energy expenditure did not differ between T2DM and controls at baseline and, in contrast to plasma BA levels, was unaffected by treatment with the BA sequestrant. Total BA as well as individual BA species did not correlate with energy expenditure at any time throughout the study. Patients with cirrhosis displayed on average an increase in energy expenditure of 18% compared to values predicted by the Harris-Benedict equation, and plasma levels of total BA (up to 12-fold) and individual BA (up to 20-fold) were increased over a wide range. However, neither total nor individual plasma BA levels correlated with energy expenditure. In addition, energy expenditure was identical in patients with a cholestatic versus a non-cholestatic origin of liver disease while plasma total BA levels differed four-fold between the groups. In conclusion, in the various (patho)physiological conditions studied, plasma BA levels were not associated with changes in energy expenditure. Therefore, our data do not support an important role of circulating BA in the control of human energy metabolism.

Provision of nutritional support to those experiencing complications following bariatric surgery

This review details the practicalities of providing nutrition support to obese patients who experience complications following bariatric surgery and highlights some of the nutritional challenges encountered by this group of patients. Bariatric surgery to treat morbid obesity has significantly increased internationally over the past decade with hospital admissions rising annually. The gastric bypass is currently the most commonly performed procedure. The complication rate can be up to 16%, with a considerable proportion having nutritional implications. The treatment can involve avoidance of oral diet and nutrition support, i.e. enteral or parenteral nutrition. Opposition to nutrition support can be encountered. It is useful to clarify the aims of nutrition support, these being: the avoidance of overfeeding and its consequences, preservation of lean body mass and promotion of healing. Evidence suggests that hypoenergic nutrition is not harmful and may actually be beneficial. There is a lack of consensus regarding the optimum method to predict the nutritional requirements in the obese acutely unwell patient. The literature suggests that the predicted equations are fairly accurate compared to measured energy expenditure in free living obese patients before and after bariatric surgery. However, these findings cannot be directly applied to those obese patients experiencing complications of bariatric surgery, who will be acutely unwell exhibiting inflammatory response. It is therefore necessary to refer to the literature on energy expenditure in hospitalized obese patients, to help guide practice. More research examining the energy and protein requirements of obese patients needing nutrition support following bariatric surgery is urgently required.

Changes in neurohormonal gut peptides following bariatric surgery

The rising prevalence of obesity has reached pandemic proportions, with an associated cost estimated at up to 7% of health expenditures worldwide. Bariatric surgery is currently the only effective long-term treatment for obesity and obesity-related co-morbidities in clinically severely obese patients. However, the precise physiological mechanisms underlying the postsurgical reductions in caloric intake and body weight are poorly comprehended. It has been suggested that changes in hormones involved in hunger, food intake and satiety via the neurohormonal network may contribute to the efficacy of bariatric procedures. In this review, we consider how gastrointestinal hormone concentrations, involved in appetite and body weight regulation via the gut-brain axis, are altered by different bariatric procedures. Special emphasis is placed on neurohormonal changes following Roux-en-Y gastric bypass surgery, which is the most common and effective procedure used today.

Relative changes in resting energy expenditure during weight loss: a systematic review

A more comprehensive understanding of the effects of weight loss on the changes in resting energy expenditure (EE) is relevant. A MEDLINE search was performed to identify studies with information relevant to this systematic review. From this search, the mean rate of resting EE decrease relative to weight loss was calculated from 90 available publications. A decrease of resting EE relative to weight loss of -15.4 +/- 8.7 kcal kg(-1) was observed from 2977 [corrected] subjects. No sex differences were noted in the overall resting EE decrease relative to weight loss. However, a significant sex differences was seen with pharmacological interventions, which seemed to depress the resting EE relative to weight loss to a greater extent in men than in women (P < 0.05). A greater drop in resting EE relative to weight loss was observed for short interventions (more than 2 but less than 6 weeks) when compared with long interventions (<6 weeks) (-27.7 +/- 6.7 vs. -12.8 +/- 7.1 kcal kg(-1)) (P < 0.001). Men and women have a similar decrease in resting EE relative to weight loss except in the case of pharmacological interventions. Short interventions also produced greater resting EE losses relative to weight loss.

Gastric bypass increases energy expenditure in rats

BACKGROUND & AIMS

Mechanisms underlying weight loss maintenance after gastric bypass are poorly understood. Our aim was to examine the effects of gastric bypass on energy expenditure in rats.

METHODS

Thirty diet-induced obese male Wistar rats underwent either gastric bypass (n = 14), sham-operation ad libitum fed (n = 8), or sham-operation body weight-matched (n = 8). Energy expenditure was measured in an open circuit calorimetry system.

RESULTS

Twenty-four-hour energy expenditure was increased after gastric bypass (4.50 +/- 0.04 kcal/kg/h) compared with sham-operated, ad libitum fed (4.29 +/- 0.08 kcal/kg/h) and sham-operated, body weight-matched controls (3.98 +/- 0.10 kcal/kg/h, P < .001). Gastric bypass rats showed higher energy expenditure during the light phase than sham-operated control groups (sham-operated, ad libitum fed: 3.63 +/- 0.04 kcal/kg/h vs sham-operated, body weight-matched: 3.42 +/- 0.05 kcal/kg/h vs bypass: 4.12 +/- 0.03 kcal/kg/h, P < .001). Diet-induced thermogenesis was elevated after gastric bypass compared with sham-operated, body weight-matched controls 3 hours after a test meal (0.41% +/- 1.9% vs 10.5% +/- 2.0%, respectively, P < .05). The small bowel of gastric bypass rats was 72.1% heavier because of hypertrophy compared with sham-operated, ad libitum fed rats (P < .0001).

CONCLUSIONS

Gastric bypass in rats prevented the decrease in energy expenditure after weight loss. Diet-induced thermogenesis was higher after gastric bypass compared with body weight-matched controls. Raised energy expenditure may be a mechanism explaining the physiologic basis of weight loss after gastric bypass.

Bariatric surgery for obese adolescents: should surgery be used to treat the childhood obesity epidemic?

The prevalence of pediatric obesity has greatly increased over the past several decades, affecting both males and females among all racial and ethnic groups, and bringing with it comorbidities that were only observed in adults in the past. Childhood obesity is the most alarming public health issue facing the world today. Lifestyle modifications to reverse obesity are considered the cornerstone of treatment, but compliance is often poor and results may be minimal. Thus, many adolescents are turning to bariatric surgery as a treatment for obesity and its complications. The long-term success rate, consequences and risks for the pediatric population are still unknown, as is the compliance rate with the necessary dietary modifications that are required after these procedures.