Resting metabolic rate and weight loss after bariatric surgery

Body Composition Changes in Adolescents Who Underwent Bariatric Surgery: A Systematic Review and Meta-analysis

PURPOSE OF REVIEW

The purpose of this review and meta-analysis is to characterize the changes in body composition of children and adolescents who underwent bariatric surgery and identify possible negative effects of performing this procedure during pediatric ages.

RECENT FINDINGS

Bariatric surgery in children and adolescents is an emerging strategy to promote higher and faster body weight and fat mass losses. However, possible negative effects usually observed in surgical patients' muscle-skeletal system raise a major concern perform this intervention during growth. Despite these possible issues, most experimental studies and reviews analyze bariatric surgery's effectiveness only by assessing anthropometric outcomes such as body weight and BMI, disregarding the short- and long-term impact of bariatric surgery on all body composition outcomes. Bariatric surgery is effective to reduce fat mass in adolescents, as well as body weight, waist circumference, and BMI. Significant reduction in lean mass and fat-free mass is also observed. Bone mass seems not to be impaired. All outcomes reduction were observed only in the first 12 months after surgery. Sensitivity analysis suggests possible sex and type of surgery-related differences, favoring a higher fat mass, body weight, and BMI losses in boys and in patients who underwent RYGB.

Revisiting Resting Metabolic Rate: What is the Relation to Weight Fluctuations?

PURPOSE OF REVIEW

Despite the great progress in obesity-tackling strategies, a negative energy equilibrium between energy expenditure and energy intake remains the cornerstone in obesity management. The present review article aims to shed light on the complicated interrelations of resting metabolic rate to weight fluctuations.

RECENT FINDINGS

Energy expenditure depends on body composition and is highly affected by weight changes, exerting a significant role in subsequent weight regain and underlining the metabolic resistance that people with obesity face when dealing with weight maintenance. The main tissue involved in energy expenditure is fat-free mass, as opposed to fat mass, which exerts a substantially lower impact. Although people with obesity display higher energy expenditures than their lean counterparts, these decrease substantially in the setting of weight loss. Metabolic adaptation is the difference between measured and predicted RMR after weight loss, either via lifestyle modification or after obesity surgery. Plausible explanations for this include differences in body composition, with loss of fat-free mass playing a significant role. This becomes especially apparent in the setting of rapid and massive weight loss, as in the case of bariatric surgery. A better understanding of energy expenditure pathophysiology may aid in further enhancing weight loss and promoting weight maintenance in people with obesity.

How to address weight regain after bariatric surgery in an individualized way

Bariatric surgery is the most effective obesity treatment. As a chronic and progressive disease, weight loss response to surgery will vary individually. Thus, insufficient weight loss or regain can happen after surgery, but they lack a standard definition. There are different mechanisms underlying weight regain and/or insufficient weight loss, such as genetics, maladaptive eating behaviors, and the inadequate choice of index operations, among others. Patients with weight regain or insufficient weight loss should be submitted to an individualized and comprehensive evaluation by a multidisciplinary team. This may help identify the causes and direct the appropriate treatment individually. Options for patients with insufficient weight loss and/or weight regain following bariatric surgery include repair of postoperative complications, conversion into another operation, endoscopic therapies with inconsistent outcomes, and dietary/behavioral counseling. Revision and conversion surgeries have higher complication rates than primary operations. Although there is no standard pharmacological regimen for that indication, the new agents seem efficient and safe to promote the loss of the regained weight and even be adjunctive to selected patients before they reach the plateau. This review aims to summarize the knowledge of the best approach for patients with weight regain/insufficient weight loss and suggests an algorithm to customize the approach and therapeutic options after bariatric surgery.

Beneficial Short-Term Effects of Bariatric Surgery on Nutritional Inflammatory Profile and Metabolic Biomarkers

PURPOSE

Bariatric surgery (BS) has several potential metabolic benefits. However, little is known about its impact on changes in the inflammatory potential of diet and its effect on inflammatory and metabolic markers. This study aimed to assess the short-term beneficial effects of BS on dietary inflammatory potential and inflammatory and metabolic markers.

MATERIALS AND METHODS

Participants (n = 20) were evaluated 3 months before and after BS. Body mass, body mass index, anthropometric measurements, fat mass, fat-free mass, visceral fat, skeletal muscle mass, basal metabolic rate, serum lipids, HOMA-IR, QUICKI and inflammatory markers, including leptin, adiponectin, adiponectin/leptin ratio and plasminogen activator inhibitor-1 (PAI-1), were evaluated. Diet data were collected using a 3-day diet record and the dietary inflammatory index (DII®) and energy-adjusted dietary inflammatory index (E-DIITM) scores were computed.

RESULTS

There was a reduction in DII® (2.56 vs 2.13) and E-DIITM (2.18 vs 0.45) indicating an improvement in inflammatory nutritional profile. Moreover, there were increases in the adiponectin/leptin ratio (0.08 vs 0.21) and QUICKI scores (0.31 vs 0.37), and reductions in leptin (36.66 vs 11.41 ng/ml) and HOMA-IR scores (3.93 vs 1.50). There were also improvements in body composition and anthropometric parameters.

CONCLUSIONS

BS promotes changes in metabolic profile, inflammatory state and food intake and these modifications appeared to be associated with improvements in diet-related inflammation, an increase in the adiponectin/leptin ratio and a reduction in leptin. These results contribute to knowledge on the contribution bariatric surgery can make to the treatment of obesity and the reduction of related comorbidities.

Evolution of the basal metabolic rate after Roux-en-Y gastric bypass: a systematic review and meta-analysis

Patients who undergo Roux-en-Y gastric bypass (RYGB) exhibit a reduction in total basal metabolic rate (BMR) after surgery, which seems to be intimately related to the amount of postoperative weight loss. The objective was to perform a systematic review and meta-analysis of the literature to determine and evaluate BMR changes after RYGB. The search was performed in certified databases, and the strategy was structured according to the PRISMA ScR. The quality evaluation of the articles included in this review was assessed with two different bias risk tools (ROBINS-I and NIH) according to each study design. Two meta-analyses were elaborated based on the results. 163 articles were selected (from 2016 to 2020), and 9 articles met the inclusion criteria. All of the selected studies evaluated only adult patients, mostly women. Postoperative BMR diminished in all of the included studies after surgery compared to preoperative values. The follow-up periods were 6, 12, 24 and 36 months. Eight articles were used for the meta-analysis after the quality assessment, a total of 434 participants. Compared to baseline values, mean postoperative reductions of 356.66 kcal/d after 6 months (p < 0.001) and 432.89 kcal/d (p < 0.001) after 1 year were observed. The BMR decreases during the first years after Roux-en-Y gastric bypass, especially during the first year postsurgery.

Postoperative Resting Metabolic Rate and Successful Weight Loss After Roux-en-Y Gastric Bypass

OBJECTIVE

To analyze whether changes in RMR 6 months after RYGB could be a predictor of weight loss on late follow-up.

METHODS

Prospective study of 45 individuals submitted to RYGB in a university tertiary care hospital. Body composition was evaluated by bioelectrical impedance analysis and RMR by indirect calorimetry before (T0), 6 (T1), and 36 months (T2) after surgery.

RESULTS

RMR/day was lower in T1 (1.552 ± 275 kcal/day) than in T0 (1734 ± 372 kcal/day; p < 0.001) with a return to similar values at T2 (1.795 ± 396 kcal/day; p < 0.001). In T0, there was no correlation between RMR/kg and body composition. In T1, there was a negative correlation between RMR and BW, BMI, and % FM, and a positive correlation with % FFM. The results in T2 were similar to T1. There was a significant increase in RMR/kg between T0, T1, and T2 (13.6 ± 2.2 kcal/kg, 16.9 ± 2.7 kcal/kg, and 19.9 ± 3.4 kcal/kg) in the total group and according to gender. Eighty percent of the patients who had increased RMR/kg ≥ 2 kcal at T1 achieved > 50% EWL in T2, particularly in women (odds ratio: 27.09, p < 0.037).

CONCLUSIONS

The increase in RMR/kg after RYGB is a major factor related to a satisfactory % excess weight loss on late follow-up.

Metabolic Profile and Metabolite Analyses in Extreme Weight Responders to Gastric Bypass Surgery

Background: Roux-en-Y gastric bypass (RYGB) surgery belongs to the most frequently performed surgical therapeutic strategies against adiposity and its comorbidities. However, outcome is limited in a substantial cohort of patients with inadequate primary weight loss or considerable weight regain. In this study, gut microbiota composition and systemically released metabolites were analyzed in a cohort of extreme weight responders after RYGB. Methods: Patients (n = 23) were categorized based on excess weight loss (EWL) at a minimum of two years after RYGB in a good responder (EWL 93 ± 4.3%) or a bad responder group (EWL 19.5 ± 13.3%) for evaluation of differences in metabolic outcome, eating behavior and gut microbiota taxonomy and metabolic activity. Results: Mean BMI was 47.2 ± 6.4 kg/m² in the bad vs. 26.6 ± 1.2 kg/m² in the good responder group (p = 0.0001). We found no difference in hunger and satiety sensation, in fasting or postprandial gut hormone release, or in gut microbiota composition between both groups. Differences in weight loss did not reflect in metabolic outcome after RYGB. While fecal and circulating metabolite analyses showed higher levels of propionate (p = 0.0001) in good and valerate (p = 0.04) in bad responders, respectively, conjugated primary and secondary bile acids were higher in good responders in the fasted (p = 0.03) and postprandial state (GCA, p = 0.02; GCDCA, p = 0.02; TCA, p = 0.01; TCDCA, p = 0.02; GDCA, p = 0.05; GUDCA, p = 0.04; TLCA, p = 0.04). Conclusions: Heterogenous weight loss response to RYGB surgery separates from patients’ metabolic outcome, and is linked to unique serum metabolite signatures post intervention. These findings suggest that the level of adiposity reduction alone is insufficient to assess the metabolic success of RYGB surgery, and that longitudinal metabolite profiling may eventually help us to identify markers that could predict individual adiposity response to surgery and guide patient selection and counseling.

Are Geographical Health Accessibility and Socioeconomic Deprivation Associated with Outcomes Following Bariatric Surgery? A Retrospective Study in a High-Volume Referral Bariatric Surgical Center

PURPOSE

Few studies have evaluated the association between non-clinical determinants (socioeconomic status and geographic accessibility to healthcare) and the outcomes of bariatric surgery, with conflicting results. This study aimed to evaluate this association.

METHODS

The medical records of 1599 consecutive patients who underwent either laparoscopic Roux-en-Y gastric bypass or laparoscopic sleeve gastrectomy between June 2005 and December 2017 were retrieved. All relevant data, including patient characteristics, biometric values before and after surgery, related medical problems, surgical history, medications, and habitus, for each patient were prospectively collected in a database. Logistic regressions were used to assess the influence of non-clinical determinants on surgical indications and complications. Multilevel linear or logistic regression was used to evaluate the influence of non-clinical determinants on long-term %TWL and the probability to achieve adequate weight loss (defined as a %TWL > 20% at 12 months).

RESULTS

Analysis of the 1599 medical records revealed that most geographically isolated patients were more likely to have undergone laparoscopic Roux-en-Y gastric bypass (odds ratio: 0.97; 95% confidence interval: 0.94 to 0.99; P = 0.018) and had a greater likelihood of adequate weight loss (β: 0.03; 95% CI: 0.01 to 0.05; P = 0.021). Conversely, socioeconomic status (measured by the European Deprivation Index) did not affect outcomes following bariatric surgery.

CONCLUSION

Geographical health isolation is associated with a higher probability to achieve adequate weight loss after 1 year of follow-up, while neither health isolation nor socioeconomic deprivation is associated with post-operative mortality and morbidity. This results suggests that bariatric surgery is a safe and effective tool for weight loss despite socioeconomic deprivation.

Can exercise promote additional benefits on body composition in patients with obesity after bariatric surgery? A systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Bariatric surgery is the most effective treatment for patients with severe obesity, but success rates vary substantially. Exercise is recommended after bariatric surgery to reduce weight regain but the effectiveness remains undetermined on weight loss due to conflicting results. It is also unclear what should be the optimal exercise prescription for these patients. A systematic review and meta-analysis of randomized controlled trials on the effects of exercise on body weight (BW), anthropometric measures, and body composition after bariatric surgery was performed.

METHODS

PubMed/MEDLINE®, EBSCO®, Web of Science® and Scopus® databases were searched to identify studies evaluating exercise effectiveness.

RESULTS

The analysis comprised 10 studies (n = 487 participants). Exercise favored BW (-2.51kg; p = 0.02), waist circumference (-4.14cm; p = 0.04) and body mass index (-0.84kg·m-2; p = 0.02) reduction but no improvements in body composition. Combined exercise interventions were the most effective in reducing BW (-5.50kg; p < 0.01) and body mass index (-1.86kg·m-2; p < 0.01). Interventions starting >6-months after bariatric surgery were more successful in reducing BW (-5.02kg; p < 0.01) and body mass index (-1.62kg·m-2; p < 0.01).

CONCLUSION

Exercise, combined exercise regimens and interventions starting >6-months after bariatric surgery were effective in promoting BW, waist circumference and body mass index reduction. Exercise following bariatric surgery does not seem to favor body composition improvements.

Effect of very large body mass loss on energetics, mechanics and efficiency of walking in adults with obesity: mass-driven versus behavioural adaptations

Abstract

Understanding the mechanisms involved in the higher energy cost of walking (NC_w: the energy expenditure above resting per unit distance) in adults with obesity is pivotal to optimizing the use of walking in weight management programmes. Therefore, this study aimed to investigate the mechanics, energetics and mechanical efficiency of walking after a large body mass loss induced by bariatric surgery in individuals with obesity. Nine adults (39.5 ± 8.6 year; BMI: 42.7 ± 4.6 kg m^–2) walked at five fixed speeds before (baseline) and after the bariatric surgery (post 1 and post 2). Gas exchanges were measured to obtain NC_w. A motion analysis system and instrumented treadmill were combined to assess total mechanical work (W_tot). Mechanical efficiency (W_tot NC_w^–1) was also calculated. Participants lost 25.7 ± 3.4% of their body mass at post 1 (6.6 months; P < 0.001) and 6.1 ± 4.9% more at post 2 (12 months; P = 0.014). Mass‐normalized NC_w was similar between baseline and post 1 and decreased at post 2 compared to that at baseline (−6.2 ± 2.7%) and post 1 (−8.1 ± 1.9%; P ≤ 0.007). No difference was found in mass‐normalized W_tot during follow‐up (P = 0.36). Mechanical efficiency was similar at post 1 and post 2 when compared to that at baseline (P ≥ 0.19), but it was higher (+14.1 ± 4.6%) at post 2 than at post 1 (P = 0.013). These findings showed that after a very large body mass loss, individuals with obesity may reorganize their walking pattern into a gait more similar to that of lean adults, thus decreasing their NC_w by making their muscles work more efficiently.

Key points

A higher net (above resting) energy cost of walking (lower gait economy) is observed in adults with obesity compared to lean individuals.

Understanding the mechanisms (i.e. mass driven, gait pattern and behavioural changes) involved in this extra cost of walking in adults with obesity is pivotal to optimizing the use of walking to promote daily physical activity and improve health in these individuals.

We found that very large weight loss induced by bariatric surgery significantly decreased the energy cost of walking per kg of body mass after 1 year with similar total mechanical work per kg of body mass, resulting in an increased mechanical efficiency of walking.

Individuals with obesity may reorganize their walking pattern into a gait more similar to that of adults of normal body mass, thus decreasing their energy cost of walking by making their muscles work more efficiently.

Provision of ready-to-drink protein following bariatric surgery: An evaluation of tolerability, body composition, and metabolic rate

BACKGROUND & AIMS

It is recommended that patients consume at least 60 g of dietary protein per day to attenuate loss of fat-free mass (FFM) following bariatric surgery. To date, research on the effectiveness and tolerability of protein supplementation in bariatric patients is limited. The purpose of the current study was to determine if provision of 12-weeks of daily protein supplementation was an effective and tolerable method of facilitating higher protein intakes in bariatric surgery patients. A secondary aim was to evaluate the effects of protein supplementation on body composition, metabolic rate, and functional outcomes. An exploratory aim was to compare body composition estimates from bioelectrical impedance spectroscopy and dual-energy x-ray absorptiometry.

METHODS

Bariatric surgery patients (n = 49; 88% female) (mean ± standard deviation; Age: 43.7 ± 10.7 yrs; BMI: 51.2 ± 13.7 kg m^-2) were provided with either a 12-week supply of ready-to-drink protein shakes (PRO; n = 25) or instructed to follow standard-of-care recommendations (SOC; n = 24) following surgery. Patients completed measures of body composition (fat mass [FM], percent body fat [%BF], FFM; bioelectrical impedance [BIS] and/or dual-energy x-ray absorptiometry [DXA]), resting metabolic rate (RMR; indirect calorimetry), a 30-s chair stand, and 3-day food logs prior to surgery (base), 3-weeks, 12-weeks, and 24-weeks post-surgery.

RESULTS

About 80% of all patients achieved the recommended intake of 60 g per day, with no significant differences in protein intake between groups (p < 0.05). Patients in PRO were more likely to increase protein consumption over the course of the entire intervention compared to SOC. Both groups experienced significant decreases in weight, BMI, %BF, FM, FFM, and total body water (TBW) (p < 0.05). The percentage of weight lost as FFM was significantly greater when measured by BIS (39.1%) compared to when measured by DXA (17.8%) (p < 0.05). There was a significant decrease in RMR from base-3 weeks for both groups (p = 0.002; 95% confidence interval [-370.6, -90.7]); there were no significant changes after 3 weeks (p > 0.05). The number of sit-to-stand trials increased at each testing session after the first 3 weeks (p < 0.05).

CONCLUSIONS

Patients were able to achieve the recommended 60 g of protein per day post-surgery, but the provision of ready-to-drink protein shakes may help bariatric patients achieve higher post-surgery protein intakes. Both groups experienced significant decreases in weight, BMI, and body composition; results varied depending on the method of body composition used. Changes in FFM measured by BIS may reflect greater changes in TBW as opposed to actual muscle mass. Registered at ClinicalTrials.gov, ID#NCT02951663.

Changes in bone mass and body composition after bariatric surgery

Aim: To analyze the effects of body weight loss on bone mineral density (BMD) on hip (Hip BMD) and lumbar spine (Lumbar BMD) after six months of bariatric surgery. Bariatric surgery is an effective treatment for morbid obesity. Nonetheless, there are scant data on the effect of weight bearing on bone structure.Material and methods: Seventeen obese women aged 41.2 ± 11.3 yrs. who underwent Roux-en-Y gastric bypass (RYGB) were included. Body composition assessments were performed through dual-energy X-ray absorptiometry immediately before and after 6-months RYGB. Data collected pre- and post-RYGB included total body weight, body mass index (BMI), lean body mass (LM), fat mass (FM) and bone mineral content. The pre- (PRE) and post-operative (POST) results were compared.Results: Lumbar BMD POST presented a non-significant loss of 1.8% whereas Hip BMD POST showed a significant loss of 17.8%. The analysis demonstrated that BMI and LM PRE explained 26% and 49%, respectively, of Hip BMD PRE variability. In addition, LM POST explained 30% of hip BMD POST variability and was not significant for Lumbar BMD POST.Conclusions: Obesity and rapid weight loss showed direct influence in Hip BMD after six months of bariatric surgery. However, its effect on the lumbar spine area was smaller due to the higher capacity of the spine to dissipate loads through its curvature.

Adipose Tissue Composition in Obesity and After Bariatric Surgery

The adipose tissue is a complex organ that regulates food intake and energy expenditure as well as induces low-grade inflammation. This review deals with changes in the composition and activity of the adipose organ after bariatric surgery, focusing on epicardial and ectopic fat and on relationships between white and brown adipose tissues. Postoperative improvements of ectopic fat and epicardial fat size and composition account for the metabolic recovery and the decreased cardiovascular risk. Following Roux-en-Y gastric bypass or biliopancreatic diversion, a proportional increase in the size and activity of the metabolically active brown adipose tissue was observed, most likely related to the postoperative rearrangement of the entero-hormonal pattern with an increase of GLP-1 production: this aspect would promote the postoperative weight loss and maintenance of post-surgery benefits.

Changes in resting metabolic rate and body composition due to intragastric balloon therapy

BACKGROUND

Intragastric balloon (IGB) insertion leads to dietary restriction; however, its neurohormonal actions were also described. Resting metabolic rate (RMR) adjusted for body mass (RMR/mass) seems to increase after bariatric interventions, whereas it generally decreases after caloric restriction-based therapies. However, no studies have evaluated the changes in body composition and RMR over IGB treatment.

OBJECTIVE

To evaluate the relationships between changes in body composition, RMR, RMR/mass, and RMR adjusted for fat-free mass (FFM) (RMR/FFM) over IGB treatment lasting 6 months.

SETTING

Single-center observational study.

METHODS

Twenty-one morbidly obese patients treated with IGB (143 ± 20 kg, body mass index [BMI] = 49.5 ± 7.3, 98% ± 29% percent excess weight, 43.6 ± 12.6 yr) were enrolled. Changes in body composition, RMR, RMR/mass, and RMR/FFM were evaluated between 1 month before IGB insertion (time point 1 [TP1]) and 3 months thereafter (TP2). Fourteen patients were also assessed 1 month after IGB removal (TP3).

RESULTS

There was a 9.5% reduction in weight, a 9.4% reduction in BMI, and 19.1% decrease in percent excess weight at TP2 (n = 21; P < .001); a further 6.5% reduction in weight and BMI and a 13.1% drop in percent excess weight (n = 14, P < .001) at TP3. They were accompanied by a 5.4% reduction in FFM between TP1 and TP2 (n = 21, P < .001). Compared with pretreatment values, at TP2 RMR was 12.5% lower (P < .001) but did not change thereafter. RMR/mass increased 12.4% between TP2 and TP3 (n = 14, P = .02) but on average did not change between TP1 and TP3. The results in the smaller cohort (n = 14) between TP1 and TP2 were consistent with results obtained for the entire cohort. Similar findings were obtained for RMR/FFM. The larger increases in RMR/mass between TP1 and TP3 were associated with more weight loss, larger drop in BMI, and more loss of excess weight (r < -.55, P < .03).

CONCLUSION

This is the first study to evaluate the relationship between changes in body composition and RMR over IGB treatment. IGB therapy leads to both fat and fat-free mass reductions and RMR decreases. More weight reduction is associated with larger increases in RMR/mass.

Prospective Longitudinal Trends in Body Composition and Clinical Outcomes 3 Years Following Sleeve Gastrectomy

BACKGROUND AND AIMS

Longitudinal assessment of body composition following bariatric surgery allows monitoring of health status. Our aim was to elucidate trends of anthropometric and clinical outcomes 3 years following sleeve gastrectomy (SG).

METHODS

A prospective cohort study of 60 patients who underwent SG. Anthropometrics including body composition analysis measured by multi-frequency bioelectrical impedance analysis, blood tests, liver fat content measured by abdominal ultrasound and habitual physical activity were evaluated at baseline and at 6 (M6), 12 (M12), and 36 (M36) months post-surgery.

RESULTS

Sixty patients (55% women, age 44.7 ± 8.7 years) who completed the entire follow-up were included. Fat mass (FM) was reduced significantly 1 year post-surgery (55.8 ± 11.3 to 26.7 ± 8.3 kg; P < 0.001) and then increased between 1 and 3 years post-operatively, but remained below baseline level (26.7 ± 8.3 to 33.1 ± 11.1 kg; P < 0.001). Fat free mass (FFM) decreased significantly during the first 6 months (64.7 ± 14.3 to 56.9 ± 11.8 kg; P < 0.001), slightly decreased between M6 and M12 and then reached a plateau through M36. Weight loss "failure" (< 50% excess weight loss) was noticed in 5.0% and 28.3% of patients at M12 and M36, respectively. Markers of lipid and glucose metabolism changed thereafter in parallel to the changes observed in FM, with the exception of HDL-C, which increased continuingly from M6 throughout the whole period analyzed (45.0 ± 10.2 to 59.5 ± 15.4 mg/dl; P < 0.001) and HbA1c which continued to decrease between M12 and M36 (5.5 ± 0.4 to 5.3 ± 0.4%; P < 0.001). There were marked within-person variations in trends of anthropometric and clinical parameters during the 3-year follow-up.

CONCLUSIONS

Weight regain primarily attributed to FM with no further decrease in FFM occurs between 1 and 3 years post-SG. FM increase at mid-term may underlie the recurrence of metabolic risk factors and can govern clinical interventions.

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.