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

Mechanisms of Action of Bariatric Surgery on Body Weight Regulation

Bariatric surgery is an effective treatment modality for obesity and obesity-associated complications. Weight loss after bariatric surgery was initially attributed to anatomic restriction or reduced energy absorption, but now it is understood that surgery treats obesity by influencing the subcortical areas of the brain to lower adipose tissue mass. There are three major phases of this process: initially the weight loss phase, followed by a phase where weight loss is maintained, and in a subset of patients a phase where weight is regained. These phases are characterized by altered appetitive behavior together with changes in energy expenditure. The mechanisms associated with the rearrangement of the gastrointestinal tract include central appetite control, release of gut peptides, change in microbiota and bile acids. However, the exact combination and timing of signals remain largely unknown.

Resolution of diabetes, gastrointestinal symptoms, and self-reported dietary intake after gastric bypass vs sleeve gastrectomy – a randomized study

BACKGROUND

There is a lack of randomized studies examining diabetes remission and dietary intake between patients undergoing Roux-en-Y gastric bypass (RYGB) versus sleeve gastrectomy (SG).

OBJECTIVE

To examine longitudinal differences in diabetes resolution, dietary intake, and gastrointestinal (GI) symptoms in patients with obesity and type 2 diabetes (T2D) randomized to either RYGB or SG and according to remission of T2D.

SETTING

Four hospitals in Sweden, 2 of which are university hospitals.

METHODS

Dietary intake and GI symptoms were calculated from questionnaires and morphometric differences between surgical methods and T2D remission were compared using the Student t test, effect size (ES) for parametric parameters, and Mann-Whitney U test for nonparametric parameters.

RESULTS

Five years after RYGB or SG there was no significant difference in the rate of remission of T2D between RYGB and SG (43% versus 20%, P = .176). RYGB (n = 19) patients had greater weight loss than SG patients (n = 14) (26.4 [9.5] versus 13.1 [9.6] kg, P < .001), despite reporting higher daily caloric intake (Δ 669 kcal, P = .059, ES .67) and food weight (Δ 1029 g/d, P = .003, ES 1.11). RYGB patients, compared with SG patients, also ate 1 more fruit per day (P = .023). Pooled data showed no differences between patients with and without T2D remission regarding weight loss, but those in remission drank more nonalcoholic drinks and milk.

CONCLUSIONS

Five years postoperatively, patients randomized to RYGB reported considerably higher food intake compared with SG despite lower body weight. The reason and importance of the higher food intake after RYGB compared with SG needs to be further studied.

Mechanisms of Weight Loss After Obesity Surgery

Obesity surgery remains the most effective treatment for obesity and its complications. Weight loss was initially attributed to decreased energy absorption from the gut but has since been linked to reduced appetitive behavior and potentially increased energy expenditure. Implicated mechanisms associating rearrangement of the gastrointestinal tract with these metabolic outcomes include central appetite control, release of gut peptides, change in microbiota, and bile acids. However, the exact combination and timing of signals remain largely unknown. In this review, we survey recent research investigating these mechanisms, and seek to provide insights on unanswered questions over how weight loss is achieved following bariatric surgery which may eventually lead to safer, nonsurgical weight-loss interventions or combinations of medications with surgery.

The magnitude and progress of lean body mass, fat-free mass, and skeletal muscle mass loss following bariatric surgery: A systematic review and meta-analysis

Postbariatric loss of muscle tissue could negatively affect long-term health due to its role in various bodily processes, such as metabolism and functional capacity. This meta-analysis aimed to unravel time-dependent changes in the magnitude and progress of lean body mass (LBM), fat-free mass (FFM), and skeletal muscle mass (SMM) loss following bariatric surgery. A systematic literature search was conducted in Pubmed, Embase, and Web of Science. Fifty-nine studies assessed LBM (n = 37), FFM (n = 20), or SMM (n = 3) preoperatively and ≥1 time points postsurgery. Random-effects meta-analyses were performed to determine pooled loss per outcome parameter and follow-up time point. At 12-month postsurgery, pooled LBM loss was -8.13 kg [95%CI -9.01; -7.26]. FFM loss and SMM loss were -8.23 kg [95%CI -10.74; -5.73] and -3.18 kg [95%CI -5.64; -0.71], respectively. About 55% of 12-month LBM loss occurred within 3-month postsurgery, followed by a more gradual decrease up to 12 months. Similar patterns were seen for FFM and SMM. In conclusion, >8 kg of LBM and FFM loss was observed within 1-year postsurgery. LBM, FFM, and SMM were predominantly lost within 3-month postsurgery, highlighting that interventions to mitigate such losses should be implemented perioperatively.

Meal Patterns and Food Choices of Female Rats Fed a Cafeteria-Style Diet Are Altered by Gastric Bypass Surgery

After Roux-en-Y gastric bypass surgery (RYGB), rats tend to reduce consumption of high-sugar and/or high-fat foods over time. Here, we sought to investigate the behavioral mechanisms underlying these intake outcomes. Adult female rats were provided a cafeteria diet comprised of five palatable foodstuffs varying in sugar and fat content and intake was monitored continuously. Rats were then assigned to either RYGB, or one of two control (CTL) groups: sham surgery or a nonsurgical control group receiving the same prophylactic iron treatments as RYGB rats. Post-sur-gically, all rats consumed a large first meal of the cafeteria diet. After the first meal, RYGB rats reduced intake primarily by decreasing the meal sizes relative to CTL rats, ate meals more slowly, and displayed altered nycthemeral timing of intake yielding more daytime meals and fewer nighttime meals. Collectively, these meal patterns indicate that despite being motivated to consume a cafeteria diet after RYGB, rats rapidly learn to modify eating behaviors to consume foods more slowly across the entire day. RYGB rats also altered food preferences, but more slowly than the changes in meal patterns, and ate proportionally more energy from complex carbohydrates and protein and proportionally less fat. Overall, the pattern of results suggests that after RYGB rats quickly learn to adjust their size, eating rate, and distribution of meals without altering meal number and to shift their macronutrient intake away from fat; these changes appear to be more related to postingestive events than to a fundamental decline in the palatability of food choices.

Long-term effect of bariatric surgery on body composition in patients with morbid obesity: A systematic review and meta-analysis

We performed a meta-analysis to provide quantitative estimates of fat mass (FM) and fat-free mass (FFM) changes in patients following bariatric surgery over 1 year. A systematic search of PubMed, SCOPUS and Web of Science databases was conducted; the pooled weighted mean difference (WMD) and 95% confidence intervals (CI) were calculated using a random-effects model. Thirty-four studies including Roux en-Y gastric bypass (RYGB), sleeve gastrectomy (SG) biliopancreatic diversion (BPD) and gastric banding (GB) were analyzed. RYGB decreased in body FM (-28.99 kg [31.21, -26.77]) or FM% (-12.73% [-15.14, -10.32]) or FFM (-9.97 kg [-10.93, -9.03]), which were greater than SG and GB. Moreover, the FFM% in RYGB group (11.72% [7.33, 16.11]) was more than SG (5.7% [4.44, 6.95]) and GB (8.1% [6.15, 10.05]) groups. Bariatric surgeries, especially RYGB, might be effective for a decrease in FM and maintenance of FFM in patients with morbid obesity in over 1 year.

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.

Will medications that mimic gut hormones or target their receptors eventually replace bariatric surgery?

Bariatric surgery is currently the most effective therapeutic modality through which sustained beneficial effects on weight loss and metabolic improvement are achieved. During recent years, indications for bariatric surgery have been expanded to include cases of poorly controlled type 2 (T2DM) diabetes mellitus in lesser extremes of body weight. A spectrum of the beneficial effects of surgery is attributed to robust changes of postprandial gut peptide responses that are observed post operatively. Consolidated knowledge regarding gut peptide physiology as well as emerging new evidence shedding light on the mode of action of previously overlooked gut hormones provide appealing potential obesity and T2DM therapeutic perspectives. The accumulation of evidence from the effect of exogenous administration of native gut peptides alone or in combinations to humans as well as the development of mimetic agents exerting agonistic effects on combinations of gut hormone receptors pave the way for future integrated gut peptide-based treatments, which may mimic the effects of bariatric surgery.

Remission of Type 2 Diabetes Mellitus after Bariatric Surgery: Fact or Fiction?

Although type 2 diabetes mellitus (T2DM) has been traditionally viewed as an intractable chronic medical condition, accumulating evidence points towards the notion that a complete remission of T2DM is feasible following a choice of medical and/or surgical interventions. This has been paralleled by increasing interest in the establishment of a universal definition for T2DM remission which, under given circumstances, could be considered equivalent to a “cure”. The efficacy of bariatric surgery in particular for achieving glycemic control has highlighted surgery as a candidate curative intervention for T2DM. Herein, available evidence regarding available surgical modalities and the mechanisms that drive metabolic amelioration after bariatric surgery are reviewed. Furthermore, reports from observational and randomized studies with regard to T2DM remission are reviewed, along with concepts relevant to the variety of definitions used for T2DM remission and other potential sources of discrepancy in success rates among different studies.

The pros and cons of gastric bypass surgery - The role of the Roux-limb

The prevalence of overweight and obesity has exploded in the post-industrial era. Life style interventions like dieting and exercise can induce a marked weight loss, but the main problem for most patients is to maintain the reduced body weight over time. Gastric bypass surgery is a commonly performed and very effective method for achieving a pronounced and sustained weight loss including metabolic improvements in obese patients. Despite the therapeutic successfulness there are known side-effects like chronic postprandial nausea and pain that in some patients become intractable. The pathophysiology is complex and partly unexplored. The physician or surgeon handling a patient with "post-bariatric symptoms" must be aware of the risk for symptom aggravations due to iatrogenic opioid-associated intestinal dysmotility. The present paper gives a brief overview of obesity surgery and its associated postsurgical conditions with a focus on the unexplored role of the Roux-limb following gastric bypass surgery.

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.

Anti-Obesity Therapy: from Rainbow Pills to Polyagonists

With their ever-growing prevalence, obesity and diabetes represent major health threats of our society. Based on estimations by the World Health Organization, approximately 300 million people will be obese in 2035. In 2015 alone there were more than 1.6 million fatalities attributable to hyperglycemia and diabetes. In addition, treatment of these diseases places an enormous burden on our health care system. As a result, the development of pharmacotherapies to tackle this life-threatening pandemic is of utmost importance. Since the beginning of the 19th century, a variety of drugs have been evaluated for their ability to decrease body weight and/or to improve deranged glycemic control. The list of evaluated drugs includes, among many others, sheep-derived thyroid extracts, mitochondrial uncouplers, amphetamines, serotonergics, lipase inhibitors, and a variety of hormones produced and secreted by the gastrointestinal tract or adipose tissue. Unfortunately, when used as a single hormone therapy, most of these drugs are underwhelming in their efficacy or safety, and placebo-subtracted weight loss attributed to such therapy is typically not more than 10%. In 2009, the generation of a single molecule with agonism at the receptors for glucagon and the glucagon-like peptide 1 broke new ground in obesity pharmacology. This molecule combined the beneficial anorectic and glycemic effects of glucagon-like peptide 1 with the thermogenic effect of glucagon into a single molecule with enhanced potency and sustained action. Several other unimolecular dual agonists have subsequently been developed, and, based on their preclinical success, these molecules illuminate the path to a new and more fruitful era in obesity pharmacology. In this review, we focus on the historical pharmacological approaches to treat obesity and glucose intolerance and describe how the knowledge obtained by these studies led to the discovery of unimolecular polypharmacology.

Indirect calorimetry as point of care testing

Determining energy requirement is a fundamental of nutrition support. Indirect calorimetry (IC) has been long recognized as the gold standard for assessing basal or resting energy expenditure (REE). The measurement of REE is recommended particularly in the situation where adjustment of energy provision is critical. The result of the IC measurement can lead to changes in treatment and since the change can be carried out immediately at the bedside, this may be considered as point-of-care testing. Beyond the nutritional aspects, studies of energy expenditure with IC have brought out more understanding of the metabolic changes during the natural course of diseases or conditions as well as those related to the intervention. The literature in various disease states has shown that changes in energy expenditure may reveal hidden metabolic information that might be translated into clinical information and have the potential of being both prognostic indicators and/or treatment targets.

Targeting Bile Acid-Activated Receptors in Bariatric Surgery

Bariatric surgical procedures, including Roux-en-Y gastric bypass and vertical sleeve gastrectomy, are currently the most effective clinical approaches to achieve a significant and sustainable weight loss. Bariatric surgery also concomitantly improves type 2 diabetes and other metabolic diseases such as nonalcoholic steatohepatitis, cardiovascular diseases, and hyperlipidemia. However, despite the recent exciting progress in the understanding how bariatric surgery works, the underlying molecular mechanisms of bariatric surgery remain largely unknown. Interestingly, bile acids are emerging as potential signaling molecules to mediate the beneficial effects of bariatric surgery. In this review, we summarize the recent findings on bile acids and their activated receptors in mediating the beneficial metabolic effects of bariatric surgery. We also discuss the potential to target bile acid-activated receptors in order to treat obesity and other metabolic diseases.

Biliopancreatic Diversion is associated with greater increases in energy expenditure than Roux-en-Y Gastric Bypass

Objective

The greater weight loss achieved following Biliopancreatic Diversion with Duodenal Switch (BPDS) versus Roux-en-Y Gastric Bypass (RYGB) has been attributed to the malabsorptive effects of BPDS. Increased weight loss after BPDS could also be underpinned by larger increases in energy expenditure. Hypothetically, the more radical reconfiguration of the small intestine in BPDS could result in an accentuated increase in meal associated thermogenesis (MAT).

Design

Female subjects (baseline mean age 40 years, mean BMI-55kg/m²) were assessed four years after randomization to BPDS (n = 6) or RYGB (n = 6). Energy expenditure (EE) and respiratory quotient (RQ) were measured by indirect calorimetry over 24 hours. A detailed protocol allowed for discrimination of basal metabolic rate (BMR), fasting EE and MAT as components of total energy expenditure (TEE) normalised for total and lean tissue by dual-energy x-ray absorptiometry.

Results

Median weight loss at follow-up was 1.5-fold higher following BPDS relative to RYGB, resulting in respective median BMIs of 29.5 kg/m² (21.7 to 36.7) after BPDS and 37.8 kg/m² (34.1 to 45.7) after RYGB (p = 0.015). The BPDS group had a lower fat:lean ratio compared to the RYGB group (p = 0.009). Overall 24-hour TEE adjusted for total tissue was higher in the BPDS group, as were BMR, fasting EE and MAT (all p<0.05). Differences between RYGB and BPDS in BMR and TEE were nullified when normalised for lean mass. Postprandial RQ increased significantly but to a similar extent in both groups.

Conclusion

Enhanced and prolonged MAT and lower fat:lean mass ratios after BPDS may explain relative increases in total energy expenditure as compared to RYGB.

Mechanisms in bariatric surgery: Gut hormones, diabetes resolution, and weight loss

Gastric bypass surgery leads to profound changes in the secretion of gut hormones with effects on metabolism, appetite, and food intake. Here, we discuss their contributions to the improvement in glucose tolerance and the weight loss that results from the operations. We find that the improved glucose tolerance is due the following events: a negative energy balance and resulting weight loss, which improve first hepatic and later peripheral insulin sensitivity, in combination with increased postprandial insulin secretion elicited particularly by exaggerated glucagon-like peptide-1 responses. The weight loss is due to loss of appetite resulting in reduced energy intake, and we find it probable that this process is driven by exaggerated secretion of appetite-regulating gut hormones including, but probably not limited to, glucagon-like peptide-1 and peptide-YY. The increased secretion is due to an accelerated exposure to and absorption of nutrients in the small intestine. This places the weight loss and the gut hormones in key positions with respect to the metabolic improvements after bypass surgery.

Regulation of Energy Homeostasis After Gastric Bypass Surgery

The obesity epidemic continues to escalate each year in the United States more than anywhere else in the world. The existing pharmaceutical and other nonsurgical treatments for morbid obesity produce suboptimal physiologic outcomes compared with those of Roux-en-Y gastric bypass (RYGB) surgery. RYGB has been the gold standard of bariatric surgery because the beneficial long-term outcomes, which include sustainable weight loss and type 2 diabetes mellitus (T2DM) resolution, are far superior to those obtained with other bariatric surgeries. However, the current understanding of RYGB's mechanisms of actions remains limited and incomplete. There is an urgent need to understand these mechanisms as gaining this knowledge may lead to the development of innovative and less invasive procedures and/or medical devices, which can mirror the favorable outcomes of RYGB surgery. In this review, we highlight current observations of the metabolic and physiologic events following RYGB, with a particular focus on the role of the anatomical reconfiguration of the gastrointestinal tract after RYGB.

The Gut as an Endocrine Organ: Role in the Regulation of Food Intake and Body Weight

Obesity and its related complications remain a major threat to public health. Efforts to reduce the prevalence of obesity are of paramount importance in improving population health. Through these efforts, our appreciation of the role of gut-derived hormones in the management of body weight has evolved and manipulation of this system serves as the basis for our most effective obesity interventions.

PURPOSE OF THE REVIEW

We review current understanding of the enteroendocrine regulation of food intake and body weight, focusing on therapies that have successfully embraced the physiology of this system to enable weight loss.

RECENT FINDINGS

In addition to the role of gut hormones in the regulation of energy homeostasis, our understanding of the potential influence of enteroendocrine peptides in food reward pathways is evolving. So too is the role of gut derived hormones on energy expenditure. Gut-derived hormones have the ability to alter feeding behavior. Certain obesity therapies already manipulate this system; however, our evolving understanding of the effects of enteroendocrine signals on hedonic aspects of feeding and energy expenditure may be crucial in identifying future obesity therapies.

Roles of the gut in the metabolic syndrome: an overview

The metabolic syndrome is a cluster of risk factors (central obesity, hyperglycaemia, dyslipidaemia and arterial hypertension), indicating an increased risk of diabetes, cardiovascular disease and premature mortality. The gastrointestinal tract is seldom discussed as an organ system of principal importance for metabolic diseases. The present overview connects various metabolic research lines into an integrative physiological context in which the gastrointestinal tract is included. Strong evidence for the involvement of the gut in the metabolic syndrome derives from the powerful effects of weight-reducing (bariatric) gastrointestinal surgery. In fact, gastrointestinal surgery is now recommended as a standard treatment option for type 2 diabetes in obesity. Several gut-related mechanisms that potentially contribute to the metabolic syndrome will be presented. Obesity can be caused by hampered release of satiety-signalling gut hormones, reduced meal-associated energy expenditure and microbiota-assisted harvest of energy from nondigestible food ingredients. Adiposity per se is a well-established risk factor for hyperglycaemia. In addition, a leaky gut mucosa can trigger systemic inflammation mediating peripheral insulin resistance that together with a blunted incretin response aggravates the hyperglycaemic state. The intestinal microbiota is strongly associated with obesity and the related metabolic disease states, although the mechanisms involved remain unclear. Enterorenal signalling has been suggested to be involved in the pathophysiology of hypertension and postprandial triglyceride-rich chylomicrons; in addition, intestinal cholesterol metabolism probably contributes to atherosclerosis. It is likely that in the future, the metabolic syndrome will be treated according to novel pharmacological principles interfering with gastrointestinal functionality.

Peptide YY and glucagon-like peptide-1 contribute to decreased food intake after Roux-en-Y gastric bypass surgery

BACKGROUND/OBJECTIVES

Exaggerated postprandial secretion of glucagon-like peptide-1 (GLP-1) and peptide YY (PYY) may explain appetite reduction and weight loss after Roux-en-Y gastric bypass (RYGB), but causality has not been established. We hypothesized that food intake decreases after surgery through combined actions from GLP-1 and PYY. GLP-1 actions can be blocked using the GLP-1 receptor antagonist Exendin 9-39 (Ex-9), whereas PYY actions can be inhibited by the administration of a dipeptidyl peptidase-4 (DPP-4) inhibitor preventing the formation of PYY_3-36.

SUBJECTS/METHODS

Appetite-regulating gut hormones and appetite ratings during a standard mixed-meal test and effects on subsequent ad libitum food intake were evaluated in two studies: in study 1, nine patients with type 2 diabetes were examined prospectively before and 3 months after RYGB with and without Ex-9. In study 2, 12 RYGB-operated patients were examined in a randomized, placebo-controlled, crossover design on four experimental days with: (1) placebo, (2) Ex-9, (3) the DPP-4 inhibitor, sitagliptin, to reduce formation of PYY_3-36 and (4) Ex-9/sitagliptin combined.

RESULTS

In study 1, food intake decreased by 35% following RYGB compared with before surgery. Before surgery, GLP-1 receptor blockage increased food intake but no effect was seen postoperatively, whereas PYY secretion was markedly increased. In study 2, combined GLP-1 receptor blockage and DPP-4 inhibitor mediated lowering of PYY_3-36 increased food intake by ~20% in RYGB patients, whereas neither GLP-1 receptor blockage nor DPP-4 inhibition alone affected food intake, perhaps because of concomitant marked increases in the unblocked hormone.

CONCLUSIONS

Blockade of actions from only one of the two L-cell hormones, GLP-1 and PYY_3-36, resulted in concomitant increased secretion of the other, probably explaining the absent effect on food intake on these experimental days. Combined blockade of GLP-1 and PYY actions increased food intake after RYGB, supporting that these hormones have a role in decreased food intake postoperatively.

How do patients' clinical phenotype and the physiological mechanisms of the operations impact the choice of bariatric procedure?

Bariatric surgery is currently the most effective option for the treatment of morbid obesity and its associated comorbidities. Recent clinical and experimental findings have challenged the role of mechanical restriction and caloric malabsorption as the main mechanisms for weight loss and health benefits. Instead, other mechanisms including increased levels of satiety gut hormones, altered gut microbiota, changes in bile acid metabolism, and/or energy expenditure have been proposed as explanations for benefits of bariatric surgery. Beside the standard proximal Roux-en-Y gastric bypass and the biliopancreatic diversion with or without duodenal switch, where parts of the small intestine are excluded from contact with nutrients, resectional techniques like the sleeve gastrectomy (SG) have recently been added to the armory of bariatric surgeons. The variation of weight loss and glycemic control is vast between but also within different bariatric operations. We surveyed members of the Swiss Society for the Study of Morbid Obesity and Metabolic Disorders to assess the extent to which the phenotype of patients influences the choice of bariatric procedure. Swiss bariatric surgeons preferred Roux-en-Y gastric bypass and SG for patients with type 2 diabetes mellitus and patients with a body mass index >50 kg/m², which is consistent with the literature. An SG was preferred in patients with a high anesthetic risk or previous laparotomy. The surgeons’ own experience was a major determinant as there is little evidence in the literature for this approach. Although trends will come and go, evidence-based medicine requires a rigorous examination of the proof to inform clinical practice.

Diet-induced thermogenesis in postoperatve Roux-en-Y gastric bypass patients with weight regain

BACKGROUND

Bariatric surgery has been shown to be an effective treatment for obesity. Changes in energy expenditure, especially through diet-induced thermogenesis (DIT), have been identified as one of the mechanisms to explain this success. However, not all patients are able to maintain healthy postoperative weight loss. Therefore, a question arises: In the weight regain after bariatric surgery, are these changes in energy metabolism still active?

OBJECTIVE

To investigate if weight regain after Roux-en-Y gastric bypass (RYGB) surgery is associated with a lower diet-induced thermogenesis in the late postoperative period.

SETTING

A cross-sectional study with the participants chosen from among the patients from a private practice.

METHODS

This was a cross-sectional study where 3 groups of female patients were evaluated: (1) 20 patients with a RYGB postoperative time period of at least 2 years, who kept a healthy weight after surgery (loss of at least 50% of excess weight; Healthy group); (2) 19 patients with clinically severe obesity (BMI>40 kg/m(2), without co-morbidities and>35 kg/m(2), with co-morbidities; Pre group); (3) 18 patients who experienced weight regain after RYGB (Regain group). The 3 groups were submitted to indirect calorimetry to measure resting metabolic rate (RMR), respiratory quotient (RQ), and DIT. Immediately after the RMR measurement, a mixed meal of regular consistency was offered. Ten minutes after the food intake began, energy expenditure measurements were initiated continuing throughout the following 3 postprandial hours. Body composition was evaluated using multifrequency bioelectrical impedance. In subgroups of the studied population, glucose and insulin levels were measured at baseline and at 30, 60, 90, 120, and 180 minutes after feeding. The mean area under the curve (AUC) between the 3 groups and measurements at baseline were compared using the analysis of variance (ANOVA).

RESULTS

The Healthy group had the highest weight adjusted RMR value compared with both the Pre and Regain group (23.03±3.02 kcal/kg; 16.18±2.94 kcal/kg; 17.11±3.28 kcal/kg, respectively; P<.0001). The Regain and Pre groups showed no difference for this variable. The weight-adjusted DIT (AUC 0-180 min) was about 42% and 34% higher in the Healthy group compared with the Pre and Regain groups, respectively (P<.0001). Lean body mass (kg) showed a positive correlation with the AUC of weight-adjusted DIT in the 3 groups. Multiple regression revealed that lean body mass was the only variable related to weight adjusted DIT, independent of group and other selected variables.

CONCLUSION

Weight-adjusted DIT in the Regain group was smaller compared with the Healthy group, and with no difference compared with the Pre group. The lean body mass seems to have a positive association with diet-induced thermogenesis.