Independent evolution of heart autonomic function and insulin sensitivity during weight loss

Modifications of long-term heart rate variability produced in an experimental model of diet-induced metabolic syndrome

Metabolic syndrome (MetS) has been linked to a higher prevalence of cardiac arrhythmias, the most frequent being atrial fibrillation, but the mechanisms are not well understood. One possible underlying mechanism may be an abnormal modulation of autonomic nervous system activity, which can be quantified by analysing heart rate variability (HRV). Our aim was to investigate the modifications of long-term HRV in an experimental model of diet-induced MetS to identify the early changes in HRV and the link between autonomic dysregulation and MetS components. NZW rabbits were randomly assigned to control (n = 10) or MetS (n = 10) groups, fed 28 weeks with high-fat, high-sucrose diet. 24-hour recordings were used to analyse HRV at week 28 using time-domain, frequency-domain and nonlinear analyses. Time-domain analysis showed a decrease in RR interval and triangular index (Ti). In the frequency domain, we found a decrease in the low frequency band. Nonlinear analyses showed a decrease in DFA-α1 and DFA-α2 (detrended fluctuations analysis) and maximum multiscale entropy. The strongest association between HRV parameters and markers of MetS was found between Ti and mean arterial pressure, and Ti and left atrial diameter, which could point towards the initial changes induced by the autonomic imbalance in MetS.

Effects of Preoperative Sarcopenia-Related Parameters on Cardiac Autonomic Function in Women with Obesity Following Bariatric Surgery: A One-Year Prospective Study

OBJECTIVES

Investigate changes in blood pressure (BP) and heart rate variability (HRV) in women with and without sarcopenia-related parameters who underwent bariatric surgery (BS) during a one-year follow-up.

SUBJECTS AND METHODS

Women were separated into obesity (OB, n = 20) and women with obesity displaying sarcopenia-related parameters (SOP, n = 14) and evaluated before BS and 3, 6, and 12 months after BS. SOP was defined as low handgrip strength (HS) and/or low appendicular skeletal mass adjusted for weight (ASM/wt × 100, %) in the lowest quartile of the sample. ASM/wt × 100, % and HS were significantly lower in SOP than OB over a one-year follow-up of BS (p < 0.05).

RESULTS

There was a reduction in diastolic BP, heart rate (HR), SDHR, LF, and the LF/HF ratio (p < 0.05) and an increase in the HF band in both groups during the follow-up period (p < 0.05). SOP women had reduced root mean square differences of successive RR intervals (RMSSD) and HF band and an increased LF band and SD2/SD1 ratio compared to the OB group during the one-year follow-up (p < 0.05). ASM/wt × 100, % was negatively associated with the LF band (r = -0.24, p = 0.00) and positively associated with the HF band (r = 0.22, p = 0.01). Conversely, HS had no association with LF (r = -0.14, p = 0.09) and HF (r = 0.11, p = 0.19). ASM/wt × 100, % and HS were negatively associated with the LF/HF ratio (p < 0.05).

CONCLUSIONS

Women who underwent BS had an improved HRV over a one-year follow-up. However, the improvement in HRV variables was less pronounced in women with low muscle mass and/or HS during the follow-up period.

Progressive Additive Benefits of Prehabilitation and Subsequent Bariatric Surgery on Cardiac Autonomic Regulation as Assessed by Means of a Simple Unitary Composite Index: Preliminary Data from an Observational Study

Obesity is associated with an increased risk of several chronic comorbidities, which may also be determined by dysfunctional autonomic nervous system (ANS). The influence of bariatric surgery (BS) on ANS balance was explored in previous studies, but with high heterogeneity in both the assessment timing and methods employed. In the present observational study, we applied a clinical protocol which considers two subsequent phases. Twenty-nine non-diabetic obese subjects were studied at baseline (T0), after one month of lifestyle modification (prehabilitation) (phase 1-T1), and after eight months following BS (phase 2-T2). ANS regulation was assessed across the three study epochs by means of ANSI, a single composite percent-ranked proxy of autonomic balance, being free of gender and age bias, economical and simple to apply in a clinical setting. The aim of the present study was to investigate the effects of the clinical protocol based on prehabilitation and subsequent BS on the ANS regulation by means of ANSI. Potential intertwined correlations with metabolic parameters were also investigated. Notably, we observed a progressive improvement in ANS control, even by employing ANSI. Moreover, the reduction in the markers of sympathetic overactivity was found to significantly correlate with the amelioration in some metabolic parameters (fasting glucose, insulin levels, and waist circumference), as well as in stress and tiredness perception. In conclusion, this study provides convincing evidence that a unitary proxy of cardiac autonomic regulation (CAR) may reflect the progressive improvement in autonomic regulation following behavioral and surgical interventions in obese patients. Intriguingly, this might contribute to reducing cardiovascular and metabolic risk.

Postoperative effects of bariatric surgery on heart rate recovery and heart rate variability

Background: Several studies have reported associations between obesity and autonomic dysfunction. However, little research has investigated the effect of bariatric surgery on heart rate recovery (HRR) in the treadmill test and heart rate variability (HRV) in 24-hour Holter monitoring. We investigated the effects of bariatric surgery on HRR and HRV, which are parameters related to autonomic dysfunction. Methods: We retrospectively investigated patients who underwent bariatric surgery in 2019. The treadmill test, 24-hour Holter monitoring, and echocardiography were performed before and 6 months after surgery. We compared the changes in HRR in the treadmill test and HRV parameters such as the time domain and spectral domain in 24-hour Holter monitoring before and after surgery. Results: Of the 40 patients who underwent bariatric surgery, 25 patients had the treadmill test or 24-hour Holter monitoring both before and after surgery. Body weight and body mass index significantly decreased after surgery (112.86±24.37 kg vs. 89.10±20.26 kg, p<0.001; 39.22±5.69 kg/m2 vs. 31.00±5.09 kg/m2, p<0.001, respectively). HRR significantly increased (n=23; 43.00±20.97 vs. 64.29±18.49, p=0.001). The time domain of HRV parameters increased (n=21; standard deviation of the N-N interval 123.57±28.05 vs. 152.57±39.49, p=0.002 and mean N-N interval 791.57±88.84 vs. 869.05±126.31, p=0.002).Conclusions: Our data showed that HRR after exercise and HRV during 24-hour Holter monitoring improved after weight reduction with bariatric surgery through improved cardiac autonomic function.

Orthostatic intolerance after bariatric surgery: A systematic review and meta-analysis

There have been increased reports of orthostatic intolerance post-bariatric surgery. However, the prevalence, pathophysiology and long-term outcomes have not been well described. Therefore, we sought to summarize evidence of orthostatic intolerance after bariatric surgery. We conducted a systematic review using PubMed, Scopus, CINAHL, Cochrane Database of Systematic Reviews and the Cochrane Central Register of Controlled Trials (CENTRAL) to identify relevant articles from the date of inception until 1st April 2020. Study selection, data extraction and quality assessment of the included studies were performed independently by two reviewers. The findings of the included studies were narratively reported. When feasible, a meta-analysis was done to summarize the relevant results. We included 20 studies (n = 19 843 participants) reporting findings of 12 prospective cohort studies, 5 retrospective cohort studies, 2 cross-sectional studies and one randomized controlled trial. The 5-year cumulative incidence of orthostatic intolerance was 4.2% (one study). Common clinical presentations of orthostatic intolerance were lightheadedness, dizziness, syncope and palpitation. The pooled data suggested improvement in overall cardiac autonomic function (sympathetic and parasympathetic) post-bariatric surgery. In addition, a significant systolic blood pressure drop may reflect a reset of the balance between the sympathetic and parasympathetic nervous systems after weight loss in the pooled analysis. Existing literature on orthostatic intolerance post-bariatric surgeries was limited or of low quality, and larger studies are needed to know the true incidence of orthostatic intolerance post-bariatric surgeries and the pathophysiology. We found one study reporting the 5-years cumulative incidence of orthostatic intolerance post-bariatric surgeries as only 4.2%. This could challenge the idea of increased orthostatic intolerance prevalence post-bariatric surgeries. Registration The review protocol was registered at the International Prospective Register of Systemic Reviews PROSPERO (CRD42020170877).

Does bariatric surgery improve cardiac autonomic modulation assessed by heart rate variability? A systematic review

Our study aimed to explore the influence of bariatric surgery (BS) on heart rate (HR) variability (HRV) through a systematic review. Manuscripts were selected based on electronic searches of the MEDLINE, EMBASE, and CINAHL databases from the inception of each database up to year 2020, and followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) protocol. Searching of these studies was systematized using the Population Intervention Comparison Outcome Study Design strategy. We selected randomized and nonrandomized controlled trials and cohorts from prospective studies that reported the influence of BS on HRV. We assessed the quality rating using the Black and Downs questionnaire. Following the screening and eligibility stages, 14 studies were included in the review. All studies agreed that BS promotes an increase in parasympathetic HR control and HRV and a decrease in HR. Yet the literature does not provide evidence that these outcomes are directly caused by the surgical procedure. There is limited evidence to support that patients with type 2 diabetes have greater improvement in HRV as an interim measure, to individuals without. The decrease in insulin resistance was correlated with the increase in HRV in some studies, but, other studies are unsupportive of this outcome. Improvements in 2 metabolic parameters (e.g., leptin, N-terminal pro B-type natriuretic peptide) were connected with superior increases in HRV. This review demonstrated that BS promotes an increase in HRV, indicating improved autonomic control of HR.

Assessment of arrhythmias and cardiac autonomic tone at a relatively young age patients with obesity class III

There is no sufficient data on arrhythmias occurrence in obesity class III. The influence of hyperinsulinemia and insulin resistance on arrhythmias and cardiac autonomic tone is also of ongoing interest in these subjects. We prospectively studied 81 selected patients with body mass index >40 kg/m² , aged 34 (18-65) years. Among other examinations all subjects underwent electrocardiography and Holter monitoring with heart rate variability (HRV) and turbulence (HRT) evaluation. Controls consisted of 45 healthy, sex- and aged-matched lean volunteers. In patients median BMI was 44.5 kg/m² (40.1-58.1), benign arterial hypertension was present in 43.2% and dysglycemia in 27.2% of cases. In the group with obesity longer PR interval (P < .001) and corrected QT interval (P < .001) were observed, while in Holter monitoring no significant differences in supraventricular or ventricular arrhythmias and also bradyarrhythmias prevalence were observed in comparison to controls. In individuals with obesity HRV indices associated with sympathetic tone were significantly impaired and also abnormal HRT values (21.9 vs 0%, P = .04) were more frequently observed. There were no significant correlations between anthropometric obesity parameters and fasting insulin concentration, insulin resistance index and also HRV/HRT parameters in studied individuals. Univariate regression analysis revealed that only age influenced abnormal HRT occurrence (OR 1.69, 95%CI 1.08-2.98, P = .04). In conclusions, patients with obesity class III at a relatively young age who reported they felt healthy, do not present increased prevalence of arrhythmias, including life-threatening ones. Cardiac autonomic dysfunction is observed in these patients, however it has not been shown to be associated with anthropometric measurements.

Evaluating the Homeostasis Assessment Model Insulin Resistance and the Cardiac Autonomic System in Bariatric Surgery Patients: A Meta-Analysis

Morbid obesity is a severe chronic disease and subject to surgical methods for losing weight. This intervention is expected to drive to better quality of life and health status. Other important aspects which may be influenced are: HOMA-IR (as insulin resistance marker) and heart rate variability (as cardiac function and autonomic nervous system marker), which are independent and valid predictors of future cardiac, neurological, metabolic health. We pooled 4 studies (646 subjects) resulting to HOMA-IR and nine HRV components-grouped in those undergone to gastric bypass (RYGP) and those operated with vertical sleeve gastrectomy (SG) method. We performed a meta-analysis in patients for HOMA-IR and HRV, using Hedge's g correction of Cohen d for small samples. We concluded that RYGP favors insulin resistance decrease, whereas SG increases the vagal tone, improving cardiac function. The severity of cardiovascular diseases history suggests the selection of the surgery method: SG for the most severe cardiovascular cases and RYGP for those with higher HOMA-IR.

Bariatric Surgery Restores Cardiac and Sudomotor Autonomic C-Fiber Dysfunction towards Normal in Obese Subjects with Type 2 Diabetes

OBJECTIVE

The aim was to evaluate the impact of bariatric surgery on cardiac and sudomotor autonomic C-fiber function in obese subjects with and without Type 2 diabetes mellitus (T2DM), using sudorimetry and heart rate variability (HRV) analysis.

METHOD

Patients were evaluated at baseline, 4, 12 and 24 weeks after vertical sleeve gastrectomy or Roux-en-Y gastric bypass. All subjects were assessed using SudoscanTM to measure electrochemical skin conductance (ESC) of hands and feet, time and frequency domain analysis of HRV, Neurologic Impairment Scores of lower legs (NIS-LL), quantitative sensory tests (QST) and sural nerve conduction studies.

RESULTS

Seventy subjects completed up to 24-weeks of follow-up (24 non-T2DM, 29 pre-DM and 17 T2DM). ESC of feet improved significantly towards normal in T2DM subjects (Baseline = 56.71±3.98 vs 12-weeks = 62.69±3.71 vs 24-weeks = 70.13±2.88, p<0.005). HRV improved significantly in T2DM subjects (Baseline sdNN (sample difference of the beat to beat (NN) variability) = 32.53±4.28 vs 12-weeks = 44.94±4.18 vs 24-weeks = 49.71±5.19, p<0,001 and baseline rmsSD (root mean square of the difference of successive R-R intervals) = 23.88±4.67 vs 12-weeks = 38.06±5.39 vs 24-weeks = 43.0±6.25, p<0.0005). Basal heart rate (HR) improved significantly in all groups, as did weight, body mass index (BMI), percent body fat, waist circumference and high-density lipoprotein (HDL). Glycated hemoglobin (HbA1C), insulin and HOMA2-IR (homeostatic model assessment) levels improved significantly in pre-DM and T2DM subjects. On multiple linear regression analysis, feet ESC improvement was independently associated with A1C, insulin and HOMA2-IR levels at baseline, and improvement in A1C at 24 weeks, after adjusting for age, gender and ethnicity. Sudomotor function improvement was not associated with baseline weight, BMI, % body fat or lipid levels. Improvement in basal HR was also independently associated with A1C, insulin and HOMA2-IR levels at baseline.

CONCLUSION

This study shows that bariatric surgery can restore both cardiac and sudomotor autonomic C-fiber dysfunction in subjects with diabetes, potentially impacting morbidity and mortality.

Effect of Low-Energy Diets Differing in Fiber, Red Meat, and Coffee Intake on Cardiac Autonomic Function in Obese Individuals With Type 2 Diabetes

OBJECTIVE

The autonomic nervous system (ANS) regulates both the cardiovascular system and energy balance and is disturbed in diabetes and obesity. The effect of different approaches of caloric restriction on ANS function has not been assessed in individuals with diabetes. Thus, we sought to determine whether low-energy diets differing in fiber, red meat, and coffee intake exert differential effects on cardiac autonomic function.

RESEARCH DESIGN AND METHODS

In this randomized parallel-group pilot trial, obese patients with type 2 diabetes were randomly allocated to consume either a diet high in cereal fiber, free of red meat, and high in coffee (n = 13) or a diet low in fiber, high in red meat, and coffee free (n = 15) over 8 weeks. Eight measures of heart rate variability (HRV) indicating vagal and/or sympathetic modulation over 3 h and inflammatory markers were determined during a hyperinsulinemic-euglycemic clamp.

RESULTS

After 8 weeks, both dietary interventions resulted in a mean weight loss of 5-6 kg, a mean decline in heart rate of 4-6 bpm, and improvement in vagally mediated HRV. However, the changes in HRV parameters from baseline to 8 weeks did not differ between the groups. In the entire study cohort, incremental HRV from baseline to 8 weeks was associated with enhanced oxidative glucose utilization (P < 0.05), but not with insulin sensitivity and inflammatory markers.

CONCLUSIONS

In obese patients with type 2 diabetes, energy restriction per se over 8 weeks contributed to improved cardiac vagal function in relation to improved oxidative glucose utilization. This preliminary finding should be verified in a confirmatory trial.

Effect of a 1-Year Obesity Intervention (KLAKS Program) on Preexisting Autonomic Nervous Dysfunction in Childhood Obesity

Childhood obesity may involve autonomic nervous system dysfunction. Whether it improves following weight loss remains unclear. Thirty-one obese children (body mass index standard deviation scores 2.33 ± 0.47; age 11.2 ± 2.0) completed a 1-year lifestyle intervention (KLAKS: Concept Leipzig: Adiposity Therapy for School-Aged Children). Anthropometric/biochemical parameters and autonomic nervous system function (heart rate variability, quantitative pupillography) were assessed at baseline and follow-up. A multivariate model for changes in body mass index standard deviation scores considered age, gender, and changes in autonomic nervous system function. Weight status (Δ body mass index standard deviation scores: 0.16 [0.05, 0.29], P = .008), glycemic control, and free fatty acids (all P < .05) improved after the intervention. Redilation velocity increased by 0.22 mm/s [0.06, 0.38] (P = .008), and changes tended to be negatively associated with Δ body mass index standard deviation scores (P = .08 [-0.61, 0.03]). Relative reflex amplitude (23.4 vs 26.3, P = .004) and constriction velocity (4.97 mm/s vs 5.47 mm/s, P < .001) also improved. Our data provide preliminary evidence that lifestyle-intervention induced improvement of weight status/metabolic risk factors may ameliorate some parameters of autonomic nervous system dysfunction in childhood obesity.

Improvement of heart rate variability after decreased insulin resistance after sleeve gastrectomy for morbidly obesity patients

BACKGROUND

Morbidly obese patients display both an autonomic nervous imbalance and impaired glucose metabolism, and both of these conditions can be partially reversed after bariatric surgery. The aim of the present study was to investigate changes in heart rate variability (HRV) and glucose metabolism in patients after laparoscopic sleeve gastrectomy (SG).

METHODS

Eighteen morbidly obese patients who underwent SG were examined before surgery and at 7, 30, 90, and 180 days after surgery. Indices of HRV included time-domain, frequency-domain, and nonlinear parameters. Glucose metabolism was evaluated by the measuring levels of insulin resistance, glycated hemoglobin (HbA(1c)), and gut hormones.

RESULTS

The study included 9 men and 9 women with a mean age of 34 years. In the HRV study, the average R-R interval, median R-R interval, standard deviation of the R-R intervals, root mean squared successive difference of the R-R intervals (RMSSD), and the number of pairs of successive normal-to-normal beat intervals that differed by>50 ms significantly increased at 180 days after surgery. Regarding the frequency-domain indices, the low frequency (LF)/high frequency (HF) ratio was more balanced at 90 days after SG compared with baseline, and increases in the total power, LF band, and HF band were observed at 180 days. The assessments of insulin resistance, glucose metabolism, and gut hormones revealed not only improvements in the homeostasis model assessment of insulin resistance and HbA1c levels but also increases in the levels of glucagon-like peptide-1 at 90 and 180 days after surgery compared with baseline. A multivariable regression model revealed significantly negative associations between the perioperative changes in HOMA-IR and changes in both the RMSSD and HF band.

CONCLUSIONS

SG leads to early improvements in insulin resistance and glucose metabolism that are followed by improvements in HRV indices. Improvements in insulin resistance were associated with increases in the RMSSD and HF band index, but the mechanism of these changes require further study.

Effect of weight loss on sympatho-vagal balance in subjects with grade-3 obesity: restrictive surgery versus hypocaloric diet

Few and mostly uncontrolled studies indicate that weight loss improves heart rate variability (HRV) in grade-3 obesity. The aim of this study was to compare in grade-3 obesity surgery and hypocaloric diet on clinical and metabolic variables and on autonomic indices of HRV. Twenty-four subjects (body mass index, BMI 45.5 ± 9.13 kg/m(2)) underwent surgery (n = 12, gastric banding, LAGB) or received hypocaloric diet (n = 12, 1,000-1,200 kg/day). Clinical [BMI, systolic blood pressure (SBP) and diastolic blood pressure (DBP), heart rate] and metabolic variables [glucose, cholesterol, HDL- and LDL-cholesterol, triglycerides, AST and ALT transaminases] and 24-h Holter electrocardiographic-derived HRV parameters [R-R interval, standard deviation of R-R intervals (SDNN); low/high-frequency (LF/HF) ratio, and QT interval] were measured at baseline and after 6 months. The two groups were identical at baseline. BMI (-7.5 ± 3.57 kg/m(2), mean ± SD), glucose (-24.1 ± 26.77 mg/dL), SBP (-16.7 ± 22.19 mmHg) and DBP (-6.2 ± 8.56 mmHg) decreased in LAGB subjects (p < 0.05) and remained unchanged in controls. At 6 months, SDNN increased in LAGB subjects (+25.0 ± 37.19 ms, p < 0.05) and LF/HF ratio diminished (2.9 ± 1.84 vs. 4.9 ± 2.78; p = 0.01), with no change in controls; LF (daytime) and HF (24 h and daytime) increased in LAGB subjects, with no change in controls. Decrease in BMI correlated with SBP and DBP decrease (p < 0.05), and DBP decrease correlated with HR decrease (p < 0.05) and QT shortening (p < 0.05). Weight loss is associated with improvement of glucose metabolism, of blood pressure, and with changes in time and frequency domain parameters of HRV; all these changes indicate recovery of a more physiological autonomic control, with increase in parasympathetic and reduction in sympathetic indices of HRV.

Cardiovascular recovery following bariatric surgery in extremely obese adolescents: preliminary results using Cardiac Magnetic Resonance (CMR) Imaging

PURPOSE

Baseline cardiovascular characteristics and longitudinal changes following weight loss surgery (WLS) in adolescents are not well defined. Recent data suggest that the use of transthoracic echocardiography (TTE) for preoperative cardiac assessment may provide suboptimal imaging fidelity secondary to excessive upper body adiposity. High fidelity imaging using cardiac magnetic resonance (CMR) is an extremely useful diagnostic tool. We report the use of CMR in a cohort of extremely obese adolescents undergoing WLS.

METHODS

A retrospective analysis of adolescent WLS patients at a single institution was conducted. Data collection included mean age, sex, body mass index (BMI), and CMR measurements of left ventricular (LV) mass, LV end-diastolic volume (LVEDV), ejection fraction (EF), and myocardial perfusion reserve index (MPRI). Comparison of CMR results to normative data derived from lean subjects was performed.

RESULTS

Ten subjects (9 female), with a mean age and BMI of 17.4 ± 1.9 years and 50.33 ± 10.21 kg/m(2) respectively, were studied. When compared to age, gender, and height matched normal weight (NW) controls, the obese (OB) subjects had evidence of increased LV mass (122 ± 25 g vs. 101 ± 10 g, OB vs. NW respectively, p<0.05), and increased LVEDV (156 ± 25 mL vs. 109 ± 9 mL, p<0.05), with an average EF of 61.5% ± 5% (range 52% to 67% vs. 71% to 74% expected EF for males and females, respectively, p=0.003). In addition, 60% of the OB subjects (6/10) demonstrated adenosine-induced sub-endocardial ischemia at baseline, the majority of whom underwent WLS (n=5) resulting in complete normalization of ischemia in 60% (3/5) and partial improvement in 40% (2/5). A reduction in mean LV mass (range 2 to 12 g) following WLS was observed.

CONCLUSION

Extreme adolescent obesity is associated with significant cardiovascular abnormalities that include LV hypertrophy (i.e. increased LV mass) and LV dilatation. These findings, considered to be well-recognized cardiovascular disease risk factors in adults, were shown to be reversible after WLS in the small group of subjects studied here. Additional large-scale investigations designed to examine obesity-related cardiovascular disease in severely obese adolescents are required.

Effects of surgically induced weight loss by Roux-en-Y gastric bypass on cardiovascular autonomic nerve function

BACKGROUND

Obesity is associated with autonomic imbalance. With respect to cardiovascular autonomic dysfunction, this is characterized by reduced heart rate variability (HRV). Our objective was to determine the effect of surgically induced weight loss on cardiovascular autonomic nerve fiber function in subjects with severe obesity and examine whether an association with reduced insulin resistance exists. The setting was a hospital and private practice in the United States.

METHODS

A total of 32 morbidly obese patients (body mass index 51 ± 11 kg/m(2)) underwent laparoscopic Roux-en-Y gastric bypass. Measures of HRV (e.g., power spectral analysis, RR variation during deep breathing) were used to evaluate autonomic function before and 6 months after surgery. The homeostasis model assessment of insulin resistance index (HOMA-IR) was used to assess insulin resistance.

RESULTS

At 6 months after bariatric surgery, the patients had lost 58% excess body mass index with improvement in the HOMA-IR (3.0 ± 1.4 versus 1.1 ± .7; P < .001). Measures of RR variation during deep breathing and total spectral power, low frequency (LF) power (influenced by sympathetic and parasympathetic activity), and high frequency (HF) power (parasympathetic activity) increased with weight loss. The LF/HF ratio was lower (1.5 ± 1.5 versus .9 ± .7, P < .05) with a reduction in weight. Spectral analysis of HRV combined with spectral analysis of respiratory activity generated the respiration frequency area (RFA) and low frequency area. The RFA was increased, and the LFA/RFA ratio was reduced with weight loss. HOMA-IR and HRV did not correlate.

CONCLUSION

Surgically induced weight loss has a favorable effect on autonomic function, but it does not appear to be directly attributable to reduced insulin resistance.

Impact of bariatric surgery on comorbidities

Published data show that bariatric surgery not only leads to significant and sustained weight loss but also resolves or improves multiple comorbidities associated with morbid obesity. Evidence suggests that the earlier the intervention the better the resolution of comorbidities. Patients with metabolic syndrome and comorbidities associated with morbid obesity should be promptly referred for consideration for bariatric surgery earlier in the disease process.

Multi-factorial approach associated with a new 'on/off' Orlistat® use in a weight loss maintenance programme: 4 years follow-up

AIM

To assess the efficacy of a specific long-term programme for weight loss maintenance using a new 'on/off' Orlistat approach in obese subjects who previously lost more than 10% of their body weight.

METHODS

50 patients were followed up during 4 years; 34 completed the study. Subjects were followed up by physicians trained in obesity management. Anthropometrical, biological and psychological parameters were measured. Insulin sensitivity was evaluated by euglycaemic insulin clamp. Orlistat was given in case of weight relapse more than 2.5%. Subjects could take Orlistat on a voluntary basis for special occasions.

RESULTS

The BMI of completers remained stable (29.5 ± 0.9 vs. 30.6 ± 1.0 kg/m(2)). 73% of completers maintained 10% or more of their weight loss. Subjects from the no-regain group improved most of their parameters while the regain group did not. Insulin sensitivity was negatively linked to body weight during the follow up (p < 0.01, r(2) = 0.20). A negative relationship has been found between extent of the previous weight loss and the evolution of body weight during the 4 years follow-up (p < 0.01, r(2) = 0.26). Orlistat intake showed a body fat lowering effect (p < 0.05).

CONCLUSION

73% of subjects maintained more than 10% of their weight loss. Subject with a large weight loss amount are at high risk for weight regain. The Orlistat 'on/off' intake regarding his lowering body fat mass effect seems to be efficient.

Reduced heart rate variability correlates with insulin resistance but not with measures of obesity in population undergoing laparoscopic Roux-en-Y gastric bypass

BACKGROUND

Obesity is associated with a pathologic predominance of sympathetic over parasympathetic tone. With respect to the heart, this autonomic dysfunction presents as a decreased heart rate variability (HRV), which has been associated with increased cardiovascular morbidity. Gastric bypass (GB) reduces cardiovascular mortality, and, thus, could beneficially affect the HRV. We sought to identify the factors predictive of HRV in a severely obese population of undergoing GB at a university hospital in the United States.

METHODS

The data of all patients presenting for GB were included in a prospective database. The homeostatic model of assessment (HOMA) was used to calculate the insulin resistance and glucose disposition index. A 24-hour Holter monitor was used to assess the HRV. Measurements were repeated at 2 weeks and 6 months postoperatively. The correlations between variables were determined using linear mixed models.

RESULTS

We studied 30 patients undergoing GB. All exhibited some degree of reduced HRV that improved postoperatively. The HOMA-insulin resistance inversely correlated with the HRV, and the HOMA-glucose disposition index directly correlated with the parameters of HRV in our longitudinal models. Weight, body mass index, excess body weight, gender, and age did not correlate with HRV. Improvements in HRV correlated with reductions in the average heart rate, underscoring a postoperative increase in relative vagal tone.

CONCLUSION

HRV in the severely obese is better predicted by the degree of insulin resistance, than by the degree of obesity, age, or gender. GB led to an improvement in HRV, the magnitude of which correlated with the change in insulin resistance and glucose disposition index, but not with weight loss.