Body composition and energy metabolism following Roux-en-Y gastric bypass surgery

The effect of weight loss on hypothalamus structure and function in obese individuals: a systematic review and meta-analysis

INTRODUCTION

Obesity presents with structural and functional hypothalamic dysfunction. However, it is unclear whether weight loss can lead to hypothalamic changes. We therefore aimed to conduct a systematic review and meta-analysis to determine the effect of body mass reduction in obese individuals on hypothalamic structure and function.

METHODS

PubMed, Embase and Cochrane databases were searched for studies that reported the change in hypothalamic structure and function after weight loss. Qualitative and quantitative analyses were performed on magnetic resonance imaging techniques, medio-basal hypothalamus T2-relaxation time, blood oxygen level dependent (BOLD) contrast, voxel-based morphometry (VBM) and biomarkers including glucose, insulin, leptin, ghrelin and inflammatory markers of interleukins. Mean differences between pre- and post-weight loss and 95% confidence intervals (CIs) were pooled using random-effects models.

RESULTS

Thirteen pre-post studies were included, of which six accounted for the meta-analysis. Studies showed a favorable decrease in T2-relaxation time (n = 1), favorable change in hypothalamic activity after weight loss on BOLD contrast (n = 4), with higher peak activities after surgical weight loss (n = 2). No differences were found in the gray matter density of the hypothalamus on VBM (n = 1). Pooled mean differences between pre- and post-surgical weight loss revealed a decrease of 8.53 mg/dl (95% CI: 5.17, 11.9) in glucose, 7.73 pmol/l (95% CI: 5.07, 10.4) in insulin, 15.5 ng/ml (95% CI: 9.40, 21.6) in leptin, 142.9 pg/ml (95% CI: 79.0, 206.8) in ghrelin and 9.43 pg/ml (95% CI: -6.89, 25.7) in IL-6 level.

CONCLUSIONS

Our study showed weight reduction in obesity led to limited structural change and significant functional changes in the hypothalamus.

Physiology of the weight-loss plateau in response to diet restriction, GLP-1 receptor agonism, and bariatric surgery

OBJECTIVE

The objective of this study was to investigate why different weight-loss interventions result in varying durations of weight loss prior to approaching plateaus.

METHODS

A validated mathematical model of energy metabolism and body composition dynamics was used to simulate mean weight- and fat-loss trajectories in response to diet restriction, semaglutide 2.4 mg, tirzepatide 10 mg, and Roux-en-Y gastric bypass (RYGB) surgery interventions. Each intervention was simulated by adjusting two model parameters affecting energy intake to fit the mean weight-loss data. One parameter represented the persistent shift of the system from baseline equilibrium, and the other parameter represented the strength of the feedback control circuit relating weight loss to increased appetite.

RESULTS

RYGB surgery resulted in a persistent intervention magnitude more than threefold greater than diet restriction and about double that of tirzepatide and semaglutide. All interventions except diet restriction substantially weakened the appetite feedback control circuit, resulting in an extended period of weight loss prior to the plateau.

CONCLUSIONS

These preliminary mathematical modeling results suggest that both glucagon-like peptide 1 (GLP-1) receptor agonism and RYGB surgery interventions act to weaken the appetite feedback control circuit that regulates body weight and induce greater persistent effects to shift the body weight equilibrium compared with diet restriction.

Muscle Strength of Lower Limbs as a Postoperative Predictor in Bariatric Surgery

OBJECTIVE

The aim of our study was to assess postoperative lower limbs muscle strength (MS) as a predictor of late surgical success (36 months).

METHODS

Body composition analyses and isokinetic dynamometry evaluation were performed before (T0: n=123), six months (T1: n=123) and 36 months (T2: n=79) after Roux-en-y gastric bypass (RYGB). Surgical success (SS) was defined as ≥ 50% excess weight loss (EWL) 36 months after surgery or ≤ 50% surgical failure (SF).

RESULTS

There was no difference between relative MS extension (Ext) and flexion (Flex) in T1 and T2. There was also, no difference between relative MS Ext and Flex in T1 and T2 between patients with SS and SF. There was a difference in relative MS Ext (144.9 ± 39.8 Nm/kg x 125.5 ± 29.2 Nm/kg; p=0.04) and Flex (73.6 ± 21.8 Nm/kg x 60.4 ± 15.8 Nm/kg; p=0.02) between SS and SF patients only in T2. Patients with an increment in Ext and Flex MS ≥4 Nm/kg at T1 had approximately 76% of SS at 36 months.

CONCLUSION

An increase of lower limbs MS ≥4 Nm/kg 6 months after RYGB predicts SS at 36 months.

CLINICALTRIALS

gov ID: NCT04129801.

Physiology of the Weight Loss Plateau after Calorie Restriction, GLP-1 Receptor Agonism, and Bariatric Surgery

Objective

To investigate why different weight loss interventions result in varying durations of weight loss prior to approaching plateaus.

Methods

A validated mathematical model of energy balance and body composition dynamics was used to simulate mean weight loss trajectories in response to intensive calorie restriction, semaglutide 2.4 mg, tirzepatide 10 mg, and Roux en-Y gastric bypass (RYGB) surgery interventions. Each intervention was simulated by varying two model parameters affecting energy intake to fit the observed mean weight loss data. One parameter represented the persistent magnitude of the intervention to shift the system from baseline equilibrium and the other parameter represented the strength of the feedback control circuit relating weight loss to increased appetite.

Results

RYGB surgery resulted in a persistent intervention magnitude more than 4-fold greater than calorie restriction and about double that of tirzepatide and semaglutide. All interventions except calorie restriction substantially weakened the appetite feedback control circuit resulting in an extended period of weight loss prior to the plateau.

Conclusions

These preliminary mathematical modeling results suggest that both GLP-1 receptor agonism and RYGB surgery interventions act to weaken the appetite feedback control circuit regulating body weight and induce greater persistent effects to shift the body weight equilibrium as compared to intensive calorie restriction.

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.

Improved Adipose Tissue Function after Single Anastomosis Duodeno-Ileal Bypass with Sleeve-Gastrectomy (SADI-S) in Diet-Induced Obesity

Bariatric surgery has been recognized as the safest and most effective procedure for controlling type 2 diabetes (T2D) and obesity in carefully selected patients. The aim of the present study was to compare the effects of Sleeve Gastrectomy (SG) and Single Anastomosis Duodenoileal Bypass with SG (SADI-S) on the metabolic profile of diet-induced obese rats. A total of 35 four-week-old male Wistar rats were submitted to surgical interventions (sham operation, SG and SADI-S) after 4 months of being fed a high-fat diet. Body weight, metabolic profile and the expression of molecules involved in the control of subcutaneous white (SCWAT), brown (BAT) and beige (BeAT) adipose tissue function were analyzed. SADI-S surgery was associated with significantly decreased amounts of total fat pads (p < 0.001) as well as better control of lipid and glucose metabolism compared to the SG counterparts. An improved expression of molecules involved in fat browning in SCWAT and in the control of BAT and BeAT differentiation and function was observed following SADI-S. Together, our findings provide evidence that the enhanced metabolic improvement and their continued durability after SADI-S compared to SG rely, at least in part, on the improvement of the BeAT phenotype and function.

Glomerular hyperfiltration

Circulating blood is filtered across the glomerular barrier to form an ultrafiltrate of plasma in the Bowman's space. The volume of glomerular filtration adjusted by time is defined as the glomerular filtration rate (GFR), and the total GFR is the sum of all single-nephron GFRs. Thus, when the single-nephron GFR is increased in the context of a normal number of functioning nephrons, single glomerular hyperfiltration results in 'absolute' hyperfiltration in the kidney. 'Absolute' hyperfiltration can occur in healthy people after high protein intake, during pregnancy and in patients with diabetes, obesity or autosomal-dominant polycystic kidney disease. When the number of functioning nephrons is reduced, single-nephron glomerular hyperfiltration can result in a GFR that is within or below the normal range. This 'relative' hyperfiltration can occur in patients with a congenitally reduced nephron number or with an acquired reduction in nephron mass consequent to surgery or kidney disease. Improved understanding of the mechanisms that underlie 'absolute' and 'relative' glomerular hyperfiltration in different clinical settings, and of whether and how the single-nephron haemodynamic and related biomechanical forces that underlie glomerular hyperfiltration promote glomerular injury, will pave the way toward the development of novel therapeutic interventions that attenuate glomerular hyperfiltration and potentially prevent or limit consequent progressive kidney injury and loss of function.

The Effects of Roux-en-Y Gastric Bypass on Glucose- vs. Fructose-Associated Conditioned Flavor Preference

In rodents, repeated single-bottle exposures to distinctly flavored isocaloric glucose and fructose solutions, two sugars with different metabolic pathways, eventually lead to a preference for the former. Because Roux-en-Y gastric bypass (RYGB) surgery decreases preference for and intake of sugar solutions in rats, we tested whether RYGB would curtail the conditioning of a preference for a glucose-paired vs. fructose-paired flavor. RYGB (♂ n=11; ♀ n=10) and sham-operated (SHAM; ♂ n=9; ♀ n=10) rats were trained with a single bottle (30 min/day) containing 8% glucose solution flavored with either 0.05% grape or cherry Kool-Aid (Glu/CS^G) or 8% fructose solution with the alternative Kool-Aid flavor (Fru/CS^F) in an alternating fashion for 8 days. To determine baseline preferences, a 4-day 30-min two-bottle test was used to assess preference for Glu/CS^G vs. Fru/CS^F before training. After training, 2-day 30-min two-bottle tests assessed preference for the a) Glu/CS^G (CS^G-flavored 8% glucose solution) vs Fru/CS^F (CS^F-flavored 8% fructose solution), b) CS^G- vs. CS^F-flavored mixture of 4% glucose & 4% fructose (isocaloric), c) CS^G- vs. CS^F-flavored 0.2% saccharin ("sweet", no calories), and d) CS^G- vs. CS^F-flavored water. During training, only male SHAM rats demonstrated progressively increased intake of Glu/CS^G over Fru/CS^F, and female SHAM rats displayed a trend. RYGB eliminated any difference in single-bottle intake of these solutions during training, regardless of sex. Like their male and female SHAM counterparts, male RYGB rats displayed a conditioned preference for the CS^G-associated stimulus in Tests 1-3. Although female RYGB rats displayed acquisition of the conditioned flavor preference in Test 1, unlike the other groups, when the differential sugar cue between the two solutions was removed in Tests 2 and 3, female rats did not display a CS^G preference. When the sugar and sweetener cues were both removed on Test 4, all groups displayed some generalization decrement. Thus, RYGB does not compromise the ability of rats to learn and express a glucose- vs. fructose-associated conditioned flavor preference when the exact CS used in training is presented in testing. The mechanistic basis for the sex difference in the effect of RYGB on the generalization decrement observed in this type of flavor preference learning warrants further study.

Fat-Free Mass and Skeletal Muscle Mass Gain Are Associated with Diabetes Remission after Laparoscopic Sleeve Gastrectomy in Males but Not in Females

Besides massive body weight loss, laparoscopic sleeve gastrectomy (LSG) causes massive lean mass, including fat-free mass (FFM) and skeletal muscle mass (SM) that present higher metabolic rates in males. This study examines sex differences in FFM and SM changes of type 2 diabetes (T2D) remission at 12 months post-LSG. This cohort study recruited 119 patients (53.7% females) with T2D and obesity (body mass index 42.2 ± 7.0 kg/m²) who underwent LSG. Fat-mass (FM) loss was higher in males than in females (−12.8 ± 6.2% vs. −9.9 ± 5.0%, p = 0.02) after one-year post-operation. Regardless of the weight-loss difference, males had higher FFM and SM gain than did females (12.8 ± 8.0 vs. 9.9 ± 5.0% p = 0.02 and 6.5 ± 4.3% vs. 4.9 ± 6.2%, p = 0.03, respectively). Positive correlations of triglyceride reduction with FM loss (r = 0.47, p = 0.01) and SM gain (r = 0.44, p = 0.02) over 12 months post-operation were observed in males who achieved T2D remission. The T2D remission rate significantly increased 16% and 26% for each additional percentage of FFM and SM gain one year after LSG, which only happened in males. Increased FFM and SM were remarkably associated with T2D remission in males, but evidence lacks for females.

Long-term body composition improvement in post-menopausal women following bariatric surgery: a cross-sectional and case-control study

OBJECTIVE

Bariatric surgery (BS) induces loss of body fat mass (FM) with an inexorable loss of lean mass (LM). Menopause leads to deleterious changes in body composition (BC) related to estrogen deficiency including LM loss and increase in total and visceral adipose tissue (VAT). This study aims to describe the long-term weight evolution of post-menopausal women after Roux-en-Y gastric bypass (RYGB) and to compare the BC between BS patients vs post-menopausal non-operated women.

DESIGN

Cross-sectional study of 60 post-menopausal women who underwent RYGB ≥2 years prior to the study with nested case-control design.

METHODS

Post-menopausal BS women were matched for age and BMI with controls. Both groups underwent DXA scan, lipids and glucose metabolism markers assessment.

RESULTS

Median follow-up was 7.5 (2-18) years. Percentage of total weight loss (TWL%) was 28.5 ± 10%. After RYGB, LM percentage of body weight (LM%) was positively associated with TWL% and negatively associated with nadir weight. Forty-one post-BS women were age- and BMI-matched with controls. Post-BS patients showed higher LM% (57.7% (±8%) vs 52.5% (±5%), P = 0.001), reduced FM% (39.4% (±8.4%) vs 45.9% (±5.4%), P < 0.01) and lower VAT (750.6 g (±496) vs 1295.3 g (±688), P < 0.01) with no difference in absolute LM compared to controls. While post-BS women showed a better lipid profile compared to controls, no difference was found in glucose markers.

CONCLUSIONS

Post-menopausal women after RYGB have a lower FM and VAT, preserved LM and a better lipid profile compared to controls. Weight loss after RYGB seems to have a persistent positive impact on metabolic health.

Identifying the Predictors of Short Term Weight Loss Failure after Roux-En-Y Gastric Bypass

INTRODUCTION

Gastric bypass surgery is a gold standard therapy for severe obesity. This study aimed to evaluate anthropometric predictors for short-term excess weight loss (EWL) after Roux-en-Y gastric bypass surgery (RYGB) in a sample of severely obese patients.

MATERIALS AND METHODS

This cohort study was conducted on severely obese candidates for RYGB bariatric surgery in Mashhad, Iran. Indirect calorimetry, anthropometric measurements, and body composition data were collected before, one, and six months after RYGB.

RESULTS

Fifty-four participants (43, 79.6% women and 11, 20.4% men) with a mean age of 39.63 ± 9.66 years participated in this study. The mean total weight and BMI loss within six months were 32.89 ± 20.22 kg and 12.37 ± 7.34 kg/m², respectively. The mean reduction in adipose tissue and fat-free mass was 24.49 kg and 7.46 kg, respectively. The mean resting metabolism rate (RMR) reduction at one and six months after RYGB was 260.49 kcal and 396.07 kcal, respectively. There was a significant difference in mean RMR between the baseline and one and six months after RYGB (p < 0.001). There was no significant gender difference in mean weight and BMI loss percentage at six months post-RYGB (p > 0.05). Baseline skeletal muscle mass (SMM), excess BMI loss (EBMIL) at first month after surgery, and baseline neck circumference (NC) could predict EWL six months after surgery.

CONCLUSION

Reduced RMR shortly after RYGB may be due to FFM reduction. Some anthropometric and their acute changes after RYGB may predict the short-term EWL in RYGB patients.

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.

Pre-Operative Bariatric Surgery Imparts An Increased Risk of Infection, Re-Admission and Operative Intervention Following Elective Instrumented Lumbar Fusion

STUDY DESIGN

Retrospective cohort study.

OBJECTIVES

To evaluate the impact of bariatric surgery on patient outcomes following elective instrumented lumbar fusion.

METHODS

A retrospective review of a prospectively collected database was performed. Patients who underwent a bariatric procedure prior to an elective instrumented lumbar fusion were evaluated. Lumbar procedures were performed at a large academic medical center from 1/1/2012 to 1/1/2018. The primary outcome was surgical site infection (SSI) requiring surgical debridement. Secondary outcomes were prolonged wound drainage requiring treatment, implant failure requiring revision, revision secondary to adjacent segment disease (ASD), and chronic pain states. A randomly selected, surgeon and comorbidity-matched group of 59 patients that underwent an elective lumbar fusion during that period was used as a control. Statistical analysis was performed using Student's two-way t-tests for continuous data, with significance defined as P < .05.

RESULTS

Twenty-five patients were identified who underwent bariatric surgery prior to elective lumbar fusion. Mean follow-up was 2.4 ± 1.9 years in the bariatric group vs. 1.5 ± 1.3 years in the control group. Patients with a history of bariatric surgery had an increased incidence of SSI that required operative debridement, revision surgery due to ASD, and a higher incidence of chronic pain. Prolonged wound drainage and implant failure were equivalent between groups.

CONCLUSION

In the present study, bariatric surgery prior to elective instrumented lumbar fusion was associated increased risk of surgical site infection, adjacent segment disease and chronic pain when compared to non-bariatric patients.

Bariatric Surgery in Adults with Obesity: the Impact on Performance, Metabolism, and Health Indices

This systematic review summarizes current evidence on the impact of bariatric surgery (BS) on physical performance, metabolic, and health indices in adults with obesity. This systematic review suggests that BS induced significant reductions in body weight, fat mass, and fat-free mass in individuals with obesity. Additionally, BS may improve many physical fitness and health indicators. Observed improvements manifest during a distinct period of time. To date, studies on BS and performance have been small in number, nonrandomized in design, and not controlled regarding gender distribution and/or post-surgery follow-up. Future studies should further investigate concerns associated with understanding of BS outcomes to improve these outcomes with potential benefits for quality of life, disability, mortality, morbidity, and overall BS success.

Improvement of glucose metabolism following rapid weight loss after bariatric surgery and its impact on reduction of visceral abdominal fat versus free fat muscle

BACKGROUND

Body fat distribution is highly associated with metabolic disturbances. Skeletal muscle plays an important role in glucose metabolism, as it serves as an important organ for glucose storage in the form of glycogen. In fact, low muscle mass has been associated with metabolic syndrome, type 2 diabetes (T2D), systemic inflammation, and decreased survival.

OBJECTIVES

To compare the relationship between visceral abdominal fat (VAF) and fat free mass (FFM) with the improved glucose metabolism after bariatric surgery.

SETTING

University hospital, United States.

METHODS

A retrospective review was performed of all patients who underwent bariatric surgery between 2011 and 2017 at a university hospital in the United States. In severely obese patients with T2D, we measured the VAF via abdominal computed tomography scan and we calculated the FFM preoperatively and at a 12-month follow-up. Data collected included baseline demographic characteristics and perioperative parameters, such as treatment for hypertension (HTN) and T2D, body mass index (BMI), glycated hemoglobin (HbA1C), glucose, and lipid profile.

RESULTS

A total of 25 patients met the inclusion criteria. The average age was 52.5 ± 11.6 years. The initial BMI was 41.41 ± 5.7 kg/m² and the postoperative BMI was 31.7 ± 6.9 kg/m² (P < .0001). The preoperative VAF volume was 184.6 ± 90.2 cm³ and the postoperative VAF volume was 93.8 ± 46.8 cm³ at the 12-month follow-up (P < .0001). The preoperative FFM was 55.2 ± 11.4 kg and the postoperative FFM was 49.1 ± 12 kg (P < .072). The preoperative HbA1C was 5.8% ± .9%, which decreased postoperatively to 5.3% ± .4% at the 12-month follow-up (P < .013).

CONCLUSION

Bariatric surgery has been demonstrated to be an effective treatment modality for severe obesity and T2D. Our results suggest that at 12 months, there is a reduction in VAF and HbA1C without a significant loss of FFM. Further prospective studies are needed to better understand these findings.

Long-Term Effects of Laparoscopic Sleeve Gastrectomy and Roux-en-Y Gastric Bypass on Body Composition and Bone Mass Density

BACKGROUND

Currently, the two most common bariatric procedures are laparoscopic sleeve gastrectomy (LSG) and laparoscopic Roux-en-Y gastric bypass (LRYGB). Long-term data comparing the two interventions in terms of their effect on body composition and bone mass density (BMD) are scarce.

OBJECTIVE

The aim of this study was to assess body composition and BMD at least 5 years after LSG and LRYGB.

SETTING

Department of Endocrinology and Nutrition, St. Claraspital Basel and St. Clara Research Ltd., Basel, Switzerland.

METHODS

Bariatric patients at least 5 years after surgery (LSG or LRYGB) were recruited, and body composition and BMD were measured by means of dual-energy X-ray absorptiometry. Data from body composition before surgery were included in the analysis. Blood samples were taken for determination of plasma calcium, parathyroid hormone, vitamin D3, alkaline phosphatase, and C-terminal telopeptide, and the individual risk for osteoporotic fracture assessed by the Fracture Risk Assessment Tool score was calculated. After surgery, all patients received multivitamins, vitamin D3, and zinc. In addition, LRYGB patients were prescribed calcium.

RESULTS

A total of 142 patients were included, 72 LSG and 70 LRYGB, before surgery: median body mass index 43.1, median age 45.5 years, 62.7% females. Follow-up after a median of 6.7 years. For LRYGB, the percentage total weight loss at follow-up was 26.3% and for LSG 24.1% (p = 0.243). LRYGB led to a slightly lower fat percentage in body composition. At follow-up, 45% of both groups had a T score at the femoral neck below -1, indicating osteopenia. No clinically relevant difference in BMD was found between the groups.

CONCLUSIONS

At 6.7 years after surgery, no difference in body composition and BMD between LRYGB and LSG was found. Deficiencies and bone loss remain an issue after both interventions and should be monitored.

Bariatric surgery affects obesity-related protein requirements

CONTEXT

Following bariatric surgery, protein deficiency intakes are reported in morbidly obese patients, whereas post-bariatric protein requirements are not specifically defined with validated method in this population.

OBJECTIVE

To assess average protein requirement (APR) in obese subjects, before, 3 months and 12 months after bariatric surgery using the validated method of nitrogen balance.

DESIGN AND SETTING

Prospective longitudinal study conducted in 21 morbidly obese patients (BMI 43.9 ± 1.4 kg/m²) before (M0), 3 months (M3) and 12 months (M12) after sleeve gastrectomy or Roux-en-Y gastric by-pass. An additional larger cross-sectional study was performed to validate APR before surgery in non-operated matched obese patients (n = 106). APR was evaluated at M0, M3, M12 by measuring 3 days dietary intakes together with losses of nitrogen in urine and stools.

MAIN OUTCOME MEASURE

APR was defined as the mean value of protein intake required to achieve balance nitrogen equilibrium.

RESULTS

Before surgery, APR in morbidly obese patients was 0.76 [95%CI, 0.66-0.92] g/kg Body Weight (BW)/d in the experimental group, and 0.74 [0.70-0.80] g/kg BW/d in the validation group. APR was 0.62 [0.51-0.75] g/kg/d at M3 and 0.87 [0.75-0.98] g/kg/d at M12, with no difference between surgical procedures. Spontaneous protein intakes were respectively 0.80 ± 0.05, 0.43 ± 0.03 and 0.71 ± 0.04 g/kg BW/d respectively at M0, M3 and M12.

CONCLUSION

This study demonstrates a temporal change in protein requirement after bariatric surgery whatever the type of surgery. Spontaneous protein intakes following bariatric surgery does not cover protein requirements for most patients, suggesting that specific dietary protein recommandations have to be adapted in obese patients with bariatric surgery.

TRIAL REGISTRATION

Clinicaltrials.gov Identifier: NCT01249326.

Anthropometrics by Three-Dimensional Photonic Scanner in Patients with Obesity Before and After Bariatric Surgery

BACKGROUND

We studied body composition by three-dimensional photonic scanning (3DPS) and metabolic biomarkers in a large ethnically diverse cohort of individuals with severe obesity before and after weight loss by Roux-en-Y gastric bypass (RYGB) or adjustable gastric banding (AGB) surgery.

MATERIALS AND METHODS

Male and female participants (n = 95) underwent 3DPS testing in the weeks preceding bariatric surgery (baseline), and 1 year after either RYGB (n = 34) or AGB (n = 9).

RESULTS

Principal component analysis showed that A1C and HDL cholesterol clustered with waist-to-hip ratio (WHR). Both RYGB and AGB surgeries led to similar improvements in A1C and lipids after 1 year. RYGB led to greater decreases in body weight, and in most anthropometric measures, compared with AGB at 1 year. However, after accounting for weight loss differences, RYGB and AGB groups did not differ in regional decreases in circumferences or volumes; the exception was a greater reduction in lean mass in RYGB compared with AGB.

CONCLUSION

Distribution of weight loss, assessed by 3DPS, did not differ between RYGB and AGB, but surgery type predicted change in lean mass at 1 year.

Mechanisms of Weight Loss After Sleeve Gastrectomy and Adjustable Gastric Banding: Far More Than Just Restriction

Obesity has reached global epidemic proportions in recent decades. Bariatric surgery is currently accepted as most effective in alleviating morbid obesity and related disorders. Sleeve gastrectomy (SG) and adjustable gastric banding (AGB) have gained popularity since the beginning of this century because of their efficacy, safety, and simplicity. SG, in particular, has emerged as the most popular bariatric procedure because of its simpler concept and shorter operative time compared with gastric bypass. Caloric restriction, however, cannot account for the sustained weight loss and improved glucose metabolism seen following SG and AGB. Other mechanisms, including changes in gastrointestinal hormone secretion, rearrangement of hypothalamic and vagal control, alteration in energy expenditure, and re-regulation of bile acid metabolism and the intestinal flora environment, are thought to contribute to the postoperative benefits. This review focuses on clinical and experimental literature addressing the potential mechanisms for SG and AGB procedures in human and animal models. Understanding such mechanisms can provide important insight into how current gastric restrictive procedures work and how future treatments of obesity, both surgical and nonsurgical, can be developed.

The Reduction of Visceral Adipose Tissue after Roux-en-Y Gastric Bypass Is more Pronounced in Patients with Impaired Glucose Metabolism

Purpose

Visceral adipose tissue (VAT) is associated with cardiometabolic risk factors and insulin resistance. The physiological mechanisms underlying the benefits of Roux-en-Y gastric bypass surgery (RYGB) on glucose metabolism remain incompletely understood. The impact of RYGB on VAT was assessed among three groups of patients stratified by their glucose tolerance before surgery.

Methods

Forty-four obese women were categorized into normoglycemia (n = 21), impaired glucose tolerance (IGT, n = 18) and diabetes (n = 5) before surgery. Body composition measured by dual-energy X-ray absorptiometry (DXA) was performed before surgery, 6 months and 12 months after.

Results

The three groups had comparable mean age (mean 38.6 ± SD 9.9) and BMI at baseline (41.9 ± 4.3 kg/m²). After 12 months, total weight loss (mean 35.1% ± 7.5) and excess weight loss (91.1% ± 25.1) were similar between groups. Pre-surgery mean VAT was significantly higher in diabetes (mean 2495 ± 616 g) than in normoglycemia (1750 ± 617 g, p = 0.02). The percentage of VAT to total body fat was significantly higher in diabetes (mean 4.4% ± 0.9) compared to normoglycemia (2.9% ± 0.8, p = 0.003). Twelve months after surgery, VAT loss was significantly greater among patients with diabetes (mean 1927 ± 413 g) compared to normoglycemia (1202 ± 450, p = 0.009).

Conclusions

RYGB leads to important VAT loss, and this loss is greater in patients with diabetes prior to surgery. As VAT is associated with insulin resistance, this reduction may account for the profound impact of this surgery on glucose metabolism.

Influence of Energy Balance on the Rate of Weight Loss Throughout One Year of Roux-en-Y Gastric Bypass: a Doubly Labeled Water Study

OBJECTIVE

To investigate the influence of changes in energy balance and body composition on the rate of weight loss throughout 1 year of Roux-en-Y gastric bypass.

METHODS

Variables were collected pre-, 6, and 12 months (M) post-surgery from 18 women (BMI ≥ 40 and ≤ 50 kg m^-2, 20 to 45 years). Total energy expenditure (TEE_m), fat-free mass (FFM), and fat mass (FM) were measured by doubly labeled water. Self-reported energy intake (EI_sr) was obtained from three non-consecutive food diaries. Metabolic adaptation was assessed via deviations from TEE predictive equation, and the calculated energy intake (EI_c) via the sum of TEE and change in body stores.

RESULTS

BMI significantly decreased (mean ± SD) from 45 ± 2 kg m^-2 to 32 ± 3 kg m^-2 at 6 M, and to 30 ± 3 kg m^-2 at 12 M after surgery. The TEE_m reduced significantly at both time points when compared with pre-surgery (6 M: - 612 ± 317 kcal day^-1; 12 M: - 447 ± 516 kcal day^-1). At 6 M, a metabolic adaptation was observed and the energy balance was - 1151 ± 195 kcal day^-1, while at 12 M it was - 332 ± 158 kcal day^-1. Changes in the values of TEE_m were associated with changes in body weight at 12 M post-surgery. A significant underreporting was observed for EI_sr (1057 ± 385 kcal day^-1) vs. EI_c (2083 ± 309 kcal day^-1) at 12 M post-operative.

CONCLUSION

The higher rate of weight loss at 6 M post-surgery was a response to energy imbalance, which was caused by high restriction in energy intake even with the presence of metabolic adaptation at this time. The EI_sr was not sufficiently accurate to assess the energy consumption of this population.

REGISTRATION OF CLINICAL TRIALS (OBSERVATIONAL STUDY)

Brazilian Clinical Trials Registry: RBR-8k5jsj. Universal Trial Number: U1111-1206-0858.

Body composition changes in diabetes and aging

Aging is associated with changes in body composition, including both fat gain and muscle loss beginning in middle age, and is associated with increased risk of type 2 diabetes. Moreover, changes in fat distribution take place in adults as they age and may contribute to the increased risk of type 2 diabetes. Recent literature has shown differences in the age-related changes in body composition by diabetes status suggesting that some of these changes might not only be a risk factor of the development of diabetes but could also be a consequence of the disease. In this article, we review the current evidence on body composition changes that take place in adults after the diagnosis of type 2 diabetes and compare them to those observed in adults without diabetes as they age. We also review the effect of various lifestyle, pharmacological, and surgical treatments that lower blood glucose on body composition in adults with type 2 diabetes.

Assessment of Body Composition in Health and Disease Using Bioelectrical Impedance Analysis (BIA) and Dual Energy X-Ray Absorptiometry (DXA): A Critical Overview

The measurement of body composition (BC) represents a valuable tool to assess nutritional status in health and disease. The most used methods to evaluate BC in the clinical practice are based on bicompartment models and measure, directly or indirectly, fat mass (FM) and fat-free mass (FFM). Bioelectrical impedance analysis (BIA) and dual energy X-ray absorptiometry (DXA) (nowadays considered as the reference technique in clinical practice) are extensively used in epidemiological (mainly BIA) and clinical (mainly DXA) settings to evaluate BC. DXA is primarily used for the measurements of bone mineral content (BMC) and density to assess bone health and diagnose osteoporosis in defined anatomical regions (femur and spine). However, total body DXA scans are used to derive a three-compartment BC model, including BMC, FM, and FFM. Both these methods feature some limitations: the accuracy of BIA measurements is reduced when specific predictive equations and standardized measurement protocols are not utilized whereas the limitations of DXA are the safety of repeated measurements (no more than two body scans per year are currently advised), cost, and technical expertise. This review aims to provide useful insights mostly into the use of BC methods in prevention and clinical practice (ambulatory or bedridden patients). We believe that it will stimulate a discussion on the topic and reinvigorate the crucial role of BC evaluation in diagnostic and clinical investigation protocols.

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.

Bone Health After Bariatric Surgery

Bariatric surgery results in long-term weight loss and improvement or resolution in obesity-related comorbidities. However, mounting evidence indicates that it adversely affects bone health. This review summarizes clinical research findings about the impact of bariatric surgery on skeletal outcomes. The literature is the largest and strongest for the Roux-en-Y gastric bypass (RYGB) procedure, as RYGB was the most commonly performed bariatric procedure worldwide until it was very recently overtaken by the sleeve gastrectomy (SG). Because SG is a newer procedure, its skeletal effects have not yet been well defined. Epidemiologic studies have now demonstrated an increased risk of fracture after RYGB and biliopancreatic diversion with duodenal switch, both of which include a malabsorptive component. As these epidemiologic data have emerged, patient-oriented studies have elucidated the bone tissue-level changes that may account for the heightened skeletal fragility. Bariatric surgery induces early and dramatic increases in biochemical markers of bone turnover. A notable feature of recent patient-oriented clinical studies is the application of advanced skeletal imaging modalities; studies address the limitations of dual-energy X-ray absorptiometry (DXA) by using quantitative computed tomography (QCT)-based modalities to examine volumetric bone mineral density and compartment-specific density and microstructure. RYGB results in pronounced declines in bone mass at the axial skeleton demonstrated by DXA and QCT, as well as at the appendicular skeleton demonstrated by high-resolution peripheral quantitative computed tomography (HR-pQCT). RYGB has detrimental effects on trabecular and cortical microarchitecture and estimated bone strength. Skeletal changes after RYGB appear early and continue even after weight loss plateaus and weight stabilizes. The skeletal effects of bariatric surgery are presumably multifactorial, and mechanisms may involve nutritional factors, mechanical unloading, hormonal factors, and changes in body composition and bone marrow fat. Clinical guidelines address bone health and may mitigate the negative skeletal effects of surgery, although more research is needed to direct and support such guidelines. © 2018 The Authors. JBMR Plus is published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

Intestinal peptide changes after bariatric and minimally invasive surgery: Relation to diabetes remission

Bariatric surgery is very effective in achieving and maintaining weight loss but it is also associated with improvement of obesity metabolic complications, primarily type 2 diabetes (T2D). Remission of T2D or at least a net improvement of glycemic control persists for at least 5 years. The bypass of duodenum and of the first portion of the jejunum up to the Treitz ligament as in Roux-en-Y Gastric Bypass (RYGB), or the bypass of the duodenum, the entire jejunum and the first tract of the ileum, such as in Bilio-Pancreatic Diversion (BPD), achieve different results on insulin sensitivity. Insulin resistance is the major driver of T2D manifesting long before insulin secretion failure. In fact, T2D development can be prevented by treatment with insulin sensitizing agents. Interestingly, RYGB improves hepatic insulin sensitivity while BPD ameliorates whole-body insulin sensitivity. Two major theories have been advocated to explain the early remission of T2D following RYGB or BPD before a meaningful weight loss takes place, the foregut and the hindgut hypotheses. The former holds that the bypass of the proximal intestine, i.e. duodenum and jejunum, prevents the secretion of signals - including nervous transmitters and hormones - promoting insulin resistance, the latter instead states that the delivery of nutrients directly into the ileum stimulates the secretion of hormones improving glucose disposal. The most studied candidate is Glucagon Like Peptide 1 (GLP1). However, while there is unambiguous evidence that GLP-1 stimulates insulin secretion, its direct action in lowering insulin resistance, independently of the effect on weight loss secondary to its satiety action, is utterly controversial. In this review we examine the effects on T2D and gastrointestinal peptide secretion produced by different types of metabolic surgery and by minimally invasive endoscopic surgery, whose utilization for the treatment of obesity and T2D is gaining wider interest and acceptance.

The Effects of Sleeve Gastrectomy and Gastric Bypass on Branched-Chain Amino Acid Metabolism 1 Year After Bariatric Surgery

BACKGROUND

Weight loss, early after Roux-en-Y gastric bypass (GB) surgery, is associated with reduced concentrations of plasma branched-chain amino acids (BCAAs) and improved insulin sensitivity. Herein, we evaluated whether changes in BCAAs and insulin sensitivity persist with weight stabilization (1 year) after GB or sleeve gastrectomy (SG).

METHODS

We prospectively examined 22 severely obese patients (mean age 40.6 ± 2.1 years, BMI 38.8 ± 1.3 kg/m(2), and 59.1 % female) who underwent SG (n = 12) or GB (n = 10) for morbid obesity. Body fat composition was measured with dual X-Ray absorptiometry and abdominal fat volume with computed tomography. BCAAs and acylcarnitines were profiled using liquid chromatography with tandem mass spectrometry. Insulin resistance was calculated using the homeostasis model assessment for insulin resistance (HOMA-IR) formula.

RESULTS

At 1-year follow-up, the decrease in BMI, body weight, total fat mass (TFM), fat free mass, and visceral adipose tissue (VAT) was similar between SG and GB. HOMA-IR was associated with BCAA concentrations, and both were decreased equally in both surgical groups. In multivariate analysis with BCAAs, TFM, and VAT as independent factors, only VAT remained significantly associated with insulin resistance.

CONCLUSIONS

The metabolic benefits from bariatric surgery, including the changes in BCAA profile, are comparable between SG and GB. The reduction in BCAAs and improvement in the AC profiles after bariatric surgery persists up to 12 months after surgery and may not be surgical related but is influenced primarily by the amount of weight loss, in particular the reduction in visceral adiposity.

Influence of gastric bypass surgery on resting energy expenditure, body composition, physical activity, and thyroid hormones in morbidly obese patients

INTRODUCTION

One way to lose weight is bariatric surgery. Various studies have shown that after Roux-en-Y gastric bypass (RYGB), resting energy expenditure (REE) decreased may be a result of changes in fat-free mass (FFM) and thyroid-stimulating hormone levels. The aim of our study was to assess changes in body composition, REE, and thyroid hormones in patients undergoing RYGB.

METHODS

A total of 42 patients participated (21 undergoing RYGB and 21 age- and weight-matched subjects as controls) in our study. Weight, body-mass index, body composition, resting metabolic rate, physical activity, and thyroid hormones were measured at baseline in cases and 3 months after surgery in case and control groups.

RESULTS

At 3 months after surgery, patients lost an average of 21.7±1.4 kg weight, and fat mass, FFM, and REE decreased significantly. REE was higher in cases compared to controls. T₄, T₃, and thyroid-stimulating hormone at 3 months after RYGB decreased, but the decrease was significant only in T₄ compared to controls. FFM was higher and fat mass lower in cases compared to controls.

CONCLUSION

We detected a meaningful difference in REE before and after surgery, but we did not detect any meaningful difference in REE between controls and cases.

Is There Association between Vitamin D Concentrations and Body Mass Index Variation in Women Submitted to Y-Roux Surgery?

OBJECTIVE

To evaluate vitamin D deficiency and body composition of women submitted to bariatric surgery and relate their body mass index variation after surgery to 25(OH)D concentrations.

METHOD

A cross-sectional and controlled study was performed including 49 obese adult volunteer women, submitted to Roux-en-Y gastric bypass (RYGB group).

COLLECTED DATA

Body mass index (BMI), self-declared ethnicity, economic condition, physical activity level, serum concentrations of 25-hydroxycholecalciferol (25(OH)D; radioimmunoassay), parathormone, and body composition by dual-energy X-ray absorptiometry (Hologic DXA-QDR-1000) were collected.

RESULTS

25(OH)D deficiency was found in 27 (55.1%) and 8 (21.1%) in the RYGB and control groups (p=0.002). Secondary hyperparathyroidism was more frequent in the RYGB group compared to the control group (15 (30.6%) versus 1 (2.6%); p=0.001). There was no relation of the studied variables and body composition with 25(OH)D deficiency. 25(OH)D concentrations were correlated (r=-0.531; p < 0.001) with BMI reduction, regardless of vitamin D supplementation.

CONCLUSION

Women submitted to bariatric surgery (RYGB) around three years ago had higher BMI and vitamin D deficiency, along with hyperparathyroidism, compared to the control group. There was no association between variables related to body composition and 25(OH)D concentrations. On the other hand, vitamin concentrations correlated negatively to BMI variation after undergoing surgery.

Whey Protein Supplementation Enhances Body Fat and Weight Loss in Women Long After Bariatric Surgery: a Randomized Controlled Trial

BACKGROUND

The ideal nutritional approach for weight regain after bariatric surgery remains unclear.

OBJECTIVE

The objective of this study is to assess the effect of whey protein supplementation on weight loss and body composition of women who regained weight 24 or more months after bariatric surgery.

METHODS

This is a 16-week open-label, parallel-group, randomized controlled trial of women who regained at least 5 % of their lowest postoperative weight after a Roux-en-Y gastric bypass (RYGB). A total of 34 participants were treated with hypocaloric diet and randomized (1:1) to receive or not supplementation with whey protein, 0.5 g/kg of the ideal body weight. The primary outcomes were changes in body weight, fat free mass (FFM), and fat mass (FM), evaluated by tetrapolar bioelectrical impedance analysis (BIA). Secondary outcomes included resting energy expenditure, blood glucose, lipids, adiponectin, interleukin 6 (IL-6), and cholecystokinin levels. Statistical analyses included generalized estimating equations adjusted for age and physical activity.

RESULTS

Fifteen patients in each group were evaluated: mean age was 45 ± 11 years, body mass index (BMI) was 35.7 ± 5.2 kg/m², and time since surgery was 69 ± 23 months. Protein intake during follow-up increased by approximately 75 % in the intervention group (p = 0.01). The intervention group presented more body weight loss (1.86 kg, p = 0.017), accounted for FM loss (2.78, p = 0.021) and no change in FFM, as compared to controls (gain of 0.42 kg of body weight and 0.6 kg of FM). No differences in secondary outcomes were observed between groups.

CONCLUSIONS

Whey protein supplementation promoted body weight and FM loss in women with long-term weight regain following RYGB.

Laparoscopic sleeve gastrectomy improves body composition and alleviates insulin resistance in obesity related acanthosis nigricans

BACKGROUND

Acanthosis nigricans (AN) has a close relationship with obesity. It is believed that obesity and AN have the common pathophysiological basis such as hyperinsulinism. This study is aimed to observe the effect of laparoscopic sleeve gastrectomy (LSG) on body composition and insulin resistance in Chinese obese patients with acanthosis nigricans.

METHODS

A total of 37 obese patients who underwent LSG in our hospital were selected for analysis. They were divided into simple obesity (OB n = 14) and obesity with acanthosis nigricans (AN n = 23) group respectively. Body composition was measured by dual-energy X-ray absorptiometry (DEXA). Anthropometric measurements and glucolipid metabolism before and 3 months post LSG were collected for analysis.

RESULTS

Patients with AN got noticeable improvement in skin condition and their AN score was significantly decreased (3.52 ± 0.79 vs. 1.48 ± 0.73, P < 0.001).Alleviated insulin resistance and more trunk fat loss than limbs' were observed in both groups (P value < 0.01). In AN group, preoperative android fat mass (FM) was positively correlated with fasting insulin and natural logarithm of HOMA-IR (LNIR) (r = 0.622, 0.608, respectively; all P < 0.01). Besides, changes in android FM and visceral adipose tissue (VAT) also showed significantly positive correlation with changes in LNIR (r = 0.588, r = 0.598, respectively; all P < 0.01).

CONCLUSIONS

LSG had a positive impact on body composition and skin condition in Chinese obese patients with AN. Loss of android FM and VAT might result in the alleviation of insulin resistance in AN patients. Android fat distribution seems to be a potential indicator of postoperative metabolic benefits for obese patients with AN.

Roux-En-Y Gastric Bypass Vs. Sleeve Gastrectomy: Balancing the Risks of Surgery with the Benefits of Weight Loss

Background

The purpose of the study was to compare weight loss, metabolic parameters, and postoperative complications in patients undergoing Roux-en-Y gastric bypass (GB) and sleeve gastrectomy (SG).

Methods

We retrospectively studied 30-day postoperative complications as well as change in weight, blood pressure, cholesterol, hemoglobin, hemoglobin A1C, and creatinine from baseline to 2, 6, 12, and 24 months postoperatively in 383 patients undergoing GB and 336 patients undergoing SG at the University of Michigan from January 2008 to November 2013. For a study population which typically has high attrition rates, there were excellent follow-up rates (706/719 at 2 months, 566/719 at 6 months, 519/719 at 12 months, and 382/719 at 24 months).

Results

Baseline characteristics were similar in both groups except for higher weight and BMI in the SG group. The GB group experienced greater total body weight loss at 6, 12, and 24 months (41.9 vs. 34.6 kg at 24 months, p < 0.0001). Excess weight loss was 69.7 and 51.7 % following GB and SG respectively at 24 months (p < 0.0001). BP improved significantly in both groups. Surgical complication rates were greater after GB (10.1 vs. 3.5 %, p = 0.0007) with no significant difference in life-threatening or potentially life-threatening complications.

Conclusions

Weight loss was greater following GB compared to SG at 2 years. The risk for surgical complications was greater following GB. Surgical intervention should be tailored to surgical risk, comorbidities, and desired weight loss.

Electronic supplementary material

The online version of this article (doi:10.1007/s11695-016-2265-2) contains supplementary material, which is available to authorized users.

Metabolic responses to exogenous ghrelin in obesity and early after Roux-en-Y gastric bypass in humans

AIMS

Ghrelin is a gastric-derived hormone that stimulates growth hormone (GH) secretion and has a multi-faceted role in the regulation of energy homeostasis, including glucose metabolism. Circulating ghrelin concentrations are modulated in response to nutritional status, but responses to ghrelin in altered metabolic states are poorly understood. We investigated the metabolic effects of ghrelin in obesity and early after Roux-en-Y gastric bypass (RYGB).

MATERIALS AND METHODS

We assessed central and peripheral metabolic responses to acyl ghrelin infusion (1 pmol kg-1  min-1 ) in healthy, lean subjects (n = 9) and non-diabetic, obese subjects (n = 9) before and 2 weeks after RYGB. Central responses were assessed by GH and pancreatic polypeptide (surrogate for vagal activity) secretion. Peripheral responses were assessed by hepatic and skeletal muscle insulin sensitivity during a hyperinsulinaemic-euglycaemic clamp.

RESULTS

Ghrelin-stimulated GH secretion was attenuated in obese subjects, but was restored by RYGB to a response similar to that of lean subjects. The heightened pancreatic polypeptide response to ghrelin infusion in the obese was attenuated after RYGB. Hepatic glucose production and hepatic insulin sensitivity were not altered by ghrelin infusion in RYGB subjects. Skeletal muscle insulin sensitivity was impaired to a similar degree in lean, obese and post-RYGB individuals in response to ghrelin infusion.

CONCLUSIONS

These data suggest that obesity is characterized by abnormal central, but not peripheral, responsiveness to ghrelin that can be restored early after RYGB before significant weight loss. Further work is necessary to fully elucidate the role of ghrelin in the metabolic changes that occur in obesity and following RYGB.

Bile acids and bariatric surgery

Bariatric surgery, specifically Roux-en-Y gastric bypass (RYGB) and vertical sleeve gastrectomy (VSG), are the most effective and durable treatments for morbid obesity and potentially a viable treatment for type 2 diabetes (T2D). The resolution rate of T2D following these procedures is between 40 and 80% and far surpasses that achieved by medical management alone. The molecular basis for this improvement is not entirely understood, but has been attributed in part to the altered enterohepatic circulation of bile acids. In this review we highlight how bile acids potentially contribute to improved lipid and glucose homeostasis, insulin sensitivity and energy expenditure after these procedures. The impact of altered bile acid levels in enterohepatic circulation is also associated with changes in gut microflora, which may further contribute to some of these beneficial effects. We highlight the beneficial effects of experimental surgical procedures in rodents that alter bile secretory flow without gastric restriction or altering nutrient flow. This information suggests a role for bile acids beyond dietary fat emulsification in altering whole body glucose and lipid metabolism strongly, and also suggests emerging roles for the activation of the bile acid receptors farnesoid x receptor (FXR) and G-protein coupled bile acid receptor (TGR5) in these improvements. The limitations of rodent studies and the current state of our understanding is reviewed and the potential effects of bile acids mediating the short- and long-term metabolic improvements after bariatric surgery is critically examined.

Fat mass, fat-free mass, and resting metabolic rate in weight-stable sleeve gastrectomy patients compared with weight-stable nonoperated patients

BACKGROUND

There is evidence that body composition and resting metabolic rate (RMR) in weight-stable patients after Roux-en-Y gastric bypass and duodenal switch is similar to that of nonoperated individuals within the same body mass index (BMI) interval. Currently, data concerning fat mass (FM), fat-free mass (FFM), and RMR on weight-stable patients after sleeve gastrectomy (SG) are lacking.

OBJECTIVES

To assess FM, FFM, and RMR, in a selected and homogenous population of weight-stable SG patients (WSSG) and compare them with those obtained from healthy normal weight-stable nonoperated (WSNO) volunteers controls of similar sex, age, and BMI.

SETTING

University hospital, Italy.

METHODS

We assessed total weight, FM, and FFM by bioelectrical impedance assay, and RMR by indirect calorimetry, in 70 WSSG patients (47 females, 23 males) at a mean follow-up of 3.2 ± 2.1 years after SG and compared them with 70 healthy WSNO volunteers, as controls (47 females, 23 males).

RESULTS

There was no significant difference between WSSG and WSNO groups concerning total weight (males, 72 ± 2.66 versus 72.8 ± 1.99 kg, P = .0254; females 65.1 ± 2.53 versus 63.7 ± 2.87 kg, P = .0139), FM (males, 17.7 ± 1.53 versus 16.7 ± 1.57 kg, P = .0341; females 19.6 ± 0.50 versus 18.5 ± 2.85 kg, P = .0104), FFM (males, 54.3 ± 3.07 versus 56.1 ± 3.30 kg; P = .049; females 45.5 ± 2.29 versus 45.1 ± 1.13 kg, P = .287), and RMR (males, 1541 ± 121.3 versus 1463 ± 74.4 kcal/d; P = .0118; females 1214 ± 54.9 versus 1250 ± 90.1 kcal/d, P = .0215).

CONCLUSION

At a mean follow-up of 3.2 ± 2.1 years after SG, WSSG patients of both sexes have a FM, FFM, and RMR comparable to that of healthy WSNO individuals within the same age and BMI interval. These findings further support bariatric surgery-induced weight loss as a physiologic process and indicate that young patients, in the setting of an adequate preoperative and postoperative specific diet and moderate physical activity, do not suffer from excessive FFM depletion after SG in the mid-term.

Effect of a randomised 12-week resistance training programme on muscular strength, cross-sectional area and muscle quality in women having undergone Roux-en-Y gastric bypass

The purpose of this study was to examine the effect of a 12-week resistance training programme on fat-free mass (FFM), muscle cross-sectional area, muscular strength and muscle quality in women who underwent Roux-en-Y gastric bypass surgery. Participants were 16 women (mean age = 44.9 ± 10.2 years) from bariatric surgical groups who were randomly assigned into either a control or an intervention group. Air displacement plethysmography measured FFM and magnetic resonance imaging measured quadriceps muscle cross-sectional area and whole thigh muscle cross-sectional area. Muscular strength and quality was assessed using an estimated 1-Repetition Maximum assessment. All measurements were collected twice, at baseline and at a 12-week follow-up. There were significantly greater improvements in leg press strength (mean differences = 55.4%, P < 0.001, Cohen's d = 2.4), leg extension strength (mean differences = 18.0%, P = 0.014, Cohen's d = 0.86) and leg press muscle quality (mean differences = 54.5%, P < 0.001, Cohen's d = 1.9) in the intervention group compared to the control group following the resistance training programme. The resistance training intervention significantly improved muscular strength and quality; however, it did not illicit changes in FFM or muscle cross-sectional area in women who underwent Roux-en-Y gastric bypass surgery.

A Systematic Review and Meta-analysis of the Effect of Gastric Bypass Surgery on Plasma Lipid Levels

BACKGROUND

Obesity-related dyslipidaemia comprises hypercholesterolaemia, hypertriglyceridaemia, low HDL-cholesterol and normal to raised LDL-cholesterol levels. 40% of morbidly obese surgical patients have dyslipidaemia. Roux-en-Y gastric bypass (RYGB) surgery has many beneficial metabolic effects, but the full impact on plasma lipids has not been clearly defined.

METHODS

A systematic review of electronic databases (Ovid; Medline; PubMed; Embase) between 1960 and March 2012 was performed using search terms including the following: obesity surgery, bariatric surgery, gastric bypass, cholesterol, lipids, triglycerides and non-esterified fatty acids. A total of 2442 manuscripts were screened. Papers with paired plasma lipid levels around RYGB surgery were included. Exclusions included the following: editorials, dual publications, n < 10, resulting in 75 papers of relevance. A meta-analysis was performed of the effect of RYGB surgery upon plasma lipids at different time points up to 4 years following surgery, using a random effects model.

RESULTS

Paired data were available for 7815 subjects around RYGB surgery for morbid obesity with a baseline BMI 48 kg/m(2) (n = 2331). There was a reduction in plasma total cholesterol and LDL-C from 1 month up to 4 years post-RYGB (p < 0.00001, p < 0.00001). Following RYGB, HDL-C increased from 1 year onwards (p < 0.00001), and triglyceride levels were reduced postoperatively from 3 months up to 4 years (p < 0.00001). NEFA levels were increased at 1 month postoperatively (p = 0.003), but from 3 months onwards did not differ from preoperative levels (p = 0.07).

CONCLUSIONS

RYGB surgery reverses the dyslipidaemia of obesity. These findings support the use of RYGB in the management of high cardiovascular risk lipid profiles in morbid obesity.

Overview on nutritional issues in bariatric surgery

PURPOSE OF REVIEW

In the context of the worldwide obesity epidemic, bariatric surgery is the only therapy associated with a sustainable weight loss and to midterm prevention of obesity-related complications. However, nutritional and behavioral multidisciplinary medical preparation, as well as long-term postoperative nutritional follow-up, is strongly advised to avoid postoperative surgical, nutritional, or psychiatric complications.

RECENT FINDINGS

Due to a long history of restrictive diets and large body weight fluctuations, preoperative nutritional assessment and correction of vitamin and trace elements deficiencies are mandatory. A rapid and massive weight loss induces the loss of muscle mass and fat-free mass that could lead to malnutrition and osteoporosis. Dietetic counseling is advised to prevent postoperative food intolerance syndrome, malnutrition, and weight regain. Protein intake should be at least 60 g/day. Planned and structured physical exercise should be systematically promoted to maintain muscle mass and bone health.

SUMMARY

Bariatric surgery is mostly successful if patients are well prepared and monitored. The perfect patients' selection remains difficult in the absence of well defined predictive criteria of success. Future research is needed to define optimal perioperative nutritional management and its influence on long-term outcome, including quality of life and healthcare-related costs.

Recent advances in metabolic and bariatric surgery

Obesity and its associated medical conditions continue to increase and add significant burden to patients, as well as health-care systems, worldwide. Bariatric surgery is the most effective treatment for severe obesity and its comorbidities, and resolution of diabetes is weight loss-independent in the case of some operations. Although these weight-independent effects are frequently described clinically, the mechanisms behind them are not well understood and remain an intense area of focus in the growing field of metabolic and bariatric surgery. Perceptions of the mechanisms responsible for the beneficial metabolic effects of metabolic/bariatric operations have shifted from being mostly restrictive and malabsorption over the last 10 to 15 years to being more neuro-hormonal in origin. In this review, we describe recent basic and clinical findings of the major clinical procedures (adjustable gastric banding, vertical sleeve gastrectomy, Roux-en-Y gastric bypass, and biliopancreatic diversion) as well as other experimental procedures (ileal interposition and bile diversion) that recapitulate many of the metabolic effects of these complex operations in a simpler fashion. As the role of bile acids and the gut microbiome on metabolism is becoming increasingly well described, their potential roles in these improvements following metabolic surgery are becoming better appreciated. Bile acid and gut microbiome changes, in light of recent developments, are discussed in the context of these surgical procedures, as well as their implications for future study.

Fat-free mass is not lower 24 months postbariatric surgery than nonoperated matched controls

OBJECTIVE

Concerns about an excessive loss of fat-free mass (FFM) after bariatric surgery prompted this comparison of operated versus matched nonoperated controls regarding FFM.

SETTING

University Hospital and University Research Unit in an urban medical center.

METHODS

Body composition with bioelectric impedance (Tanita 310, Tanita Corp, Arlington Heights, IL) was measured approximately 2 years after bariatric surgery in weight stable patients and nonoperated weight stable controls matched for body mass index (BMI), gender, and age. t tests provided comparisons. Analysis of variance was used to compare FFM changes for 4 procedures. Levene's test evaluated variance.

RESULTS

Patients (n = 252; 24.7±15 mo after surgery) and nonoperated controls (n = 252) were matched for gender (71.8% female), age (44.5±11.0 yr), and BMI (32.8±7.0 kg/m²). Patients had different surgical procedures: 107 gastric bypasses (RYGBs), 62 biliopancreatic diversions with duodenal switch (BPD/DSs), 40 adjustable gastric bands (AGBs), and 43 sleeve gastrectomies (LSGs). FFM percentage was significantly higher in the operated patients than controls, 66% versus 62%, P<.0001. For 3 procedures, the FFM was significantly higher; however, AGBs changed only 7.3 BMI units and FFM was not significantly different from their matched controls, 59.8% versus 58.2%. Across surgical groups, FFM percentage differed, P<.0001 (RYGB 66.5±9.2%, BPD/DS 74.0±9.3%, AGB 59.8±7.0%, LSG 59.6±9.3%). Variance was not different (P = .17).

CONCLUSION

Weight-reduced bariatric surgery patients have greater FFM compared with nonoperated matched controls. These findings support surgically assisted weight loss as a physiologic process and in general patients do not suffer from excessive FFM depletion after bariatric procedures.

The Impact of Vitamin D, Calcium, Protein Supplementation, and Physical Exercise on Bone Metabolism After Bariatric Surgery: The BABS Study

Laparoscopic Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG) are common and effective methods to treat severe obesity, but these procedures can adversely influence bone metabolism and areal bone mineral density (aBMD). This was a prospective 24-month single-center interventional two-arm study in 220 women and similarly aged men (median age 40.7 years) with a body mass index (BMI) >38 kg/m(2) after RYGB and SG procedures. Patients were randomized into: 1) an intervention group receiving: 28,000 IU cholecalciferol/wk for 8 weeks before bariatric surgery, 16,000 IU/wk and 1000 mg calciummonocitrate/d after surgery, daily BMI-adjusted protein supplementation and physical exercise (Nordic walking, strength perseverance, and equipment training); 2) a non-intervention group: no preoperative loading, nutritional supplementation, or obligatory physical exercise. At study endpoint, when comparing the intervention group to the non-intervention group, the relative percentage changes of serum levels of sclerostin (12.1% versus 63.8%), cross-linked C-telopeptide (CTX, 82.6% versus 158.3%), 25-OH vitamin D (13.4% versus 18.2%), phosphate (23.7% versus 32%, p < 0.001 for all), procollagen type 1 amino-terminal propeptide (P1NP, 12% versus 41.2%), intact parathyroid hormone (iPTH, -17.3% versus -7.6%), and Dickkopf-1 (-3.9% versus -8.9%, p < 0.05 for all) differed. The decline in lumbar spine, total hip and total body aBMD, changes in BMI, lean body mass (LBM), as well as changes in trabecular bone score (TBS) values (p < 0.005 for all) were less, but significantly, pronounced in the intervention group. We conclude that vitamin D loading and ongoing vitamin D, calcium, and BMI-adjusted protein supplementation in combination with physical exercise decelerates the loss of aBMD and LBM after bariatric surgery. Moreover, the well-known increases of bone turnover markers are less pronounced.