Weight Loss Curve Analysis

Preoperative Prediction of Body Mass Index of Patients with Type 2 Diabetes at 1 Year After Laparoscopic Sleeve Gastrectomy: Cross-Sectional Study

Background: Very few models predict weight loss among type 2 diabetes mellitus (T2D) patients after laparoscopic sleeve gastrectomy (LSG). This retrospective study undertook such a task. Materials and Methods: We identified all patients >18 years old with T2D who underwent primary LSG at our institution and had complete data. The training set comprised 107 patients operated upon during the period April 2011 to June 2014; the validation set comprised 134 patients operated upon during the successive chronological period, July 2014 to December 2015. Sex, age, presurgery BMI, T2D duration, number of T2D medications, insulin use, hypertension, and dyslipidemia were utilized as independent predictors of 1-year BMI. We employed regression analysis, and assessed the goodness of fit and "Residuals versus Fits" plot. Paired sample t-tests compared the observed and predicted BMI at 1 year. Results: The model comprised preoperative BMI (β = 0.757, P = 0.026) + age (β = 0.142, P < 0.0001) with adjusted R² of 0.581 (P < 0.0001), and goodness of fit showed an unbiased model with accurate prediction. The equation was: BMI value 1 year after LSG = 1.777 + 0.614 × presurgery BMI (kg/m²) +0.106 × age (years). For validation, the equation exhibited an adjusted R² 0.550 (P < 0.0001), and the goodness of fit indicated an unbiased model. The BMI predicted by the model fell within -3.78 BMI points to +2.42 points of the observed 1-year BMI. Pairwise difference between the mean 1-year observed and predicted BMI was not significant (-0.41 kg/m², P = 0.225). Conclusions: This predictive model estimates the BMI 1 year after LSG. The model comprises preoperative BMI and age. It allows the forecast of patients' BMI after surgery, hence setting realistic expectations which are critical for patient satisfaction after bariatric surgery. An attainable target motivates the patient to achieve it.

Trend of Changes in Serum Albumin and Its Relation with Sex, Age, and BMI Following Laparoscopic Mini-gastric Bypass Surgery in Morbid Obese Cases

BACKGROUND

The aim of this study is to investigate the pattern of changes in serum albumin level after mini-gastric bypass (MGB) and its association with gender, age, and body mass index (BMI) of the patients.

METHODS

This cohort study was conducted on 196 morbidly obese patients undergoing MGB followed for 1 year. The data on BMI, serum albumin level, demographic, anthropometric, biochemical variables and comorbidities were gathered before and after (3, 6, and 12 months) surgery. The trend of changes in BMI and serum albumin of the patients was investigated by repeated measures tests using general linear model (GLM) and generalized estimating equations (GEE) approaches.

RESULTS

The mean age, baseline median BMI, and albumin of the patients were 41.34 ± 11.03 years, 44.54 kg/m², and 4.00 g/dl, respectively. There was a chronologically significant trend of decline in BMI (P < 0.001). GEE demonstrated no chronologically significant trend in serum albumin (P = 0.278). The trend of changes in albumin was significantly associated only with age grouping and baseline serum albumin level (P = 0.017 and 0.001, respectively). This trend had fluctuations in patients older than 40 years with baseline serum albumin level of 3.50-3.90 g/dl. For patients with any age and baseline serum albumin level of 4.00-4.90 g/dl, this trend was stable in all periods of follow-up.

CONCLUSION

MGB is an effective technique to lose weight. The trend of changes in serum albumin level was affected by its baseline levels and age.

A simpler method for predicting weight loss in the first year after Roux-en-Y gastric bypass

Factors postulated to predict weight loss after gastric bypass surgery, include race, age, gender, technique, height, and initial weight. This paper contained 1551 gastric bypass patients (85.9% female). Operations were performed by one surgeon (MLO) at community hospitals in Southern California from 1989 to 2008 with 314 being laparoscopic and 1237 open. We created the following equation: In[percent weight] = At(2) - Bt, where t was the time after operation (days) and A and B are constants. Analysis was completed on R-software. The model fits with R(2) value 0.93 and gives patients a realistic mean target weight with a confidence interval of 95% for the first year. Conclusion. We created a curve predicting weight loss after surgery as a percentage of initial weight. Initial weight was the single most important predictor of weight loss after surgery. Other recorded variables accounted for less than 1% of variability. Unknown factors account for the remaining 6-7%.

Characterization of weight loss and weight regain mechanisms after Roux-en-Y gastric bypass in rats

Roux-en-Y gastric bypass (RYGB) is the most effective therapy for morbid obesity, but it has a ∼20% failure rate. To test our hypothesis that outcome depends on differential modifications of several energy-related systems, we used our established RYGB model in Sprague-Dawley diet-induced obese (DIO) rats to determine mechanisms contributing to successful (RGYB-S) or failed (RYGB-F) RYGB. DIO rats were randomized to RYGB, sham-operated Obese, and sham-operated obese pair-fed linked to RYGB (PF) groups. Body weight (BW), caloric intake (CI), and fecal output (FO) were recorded daily for 90 days, food efficiency (FE) was calculated, and morphological changes were determined. d-Xylose and fat absorption were studied. Glucose-stimulated vagal efferent nerve firing rates of stomach were recorded. Gut, adipose, and thyroid hormones were measured in plasma. Mitochondrial respiratory complexes in skeletal muscle and expression of energy-related hypothalamic and fat peptides, receptors, and enzymes were quantified. A 25% failure rate occurred. RYGB-S, RYGB-F, and PF rats showed rapid BW decrease vs. Obese rats, followed by sustained BW loss in RYGB-S rats. RYGB-F and PF rats gradually increased BW. BW loss in RYGB-S rats is achieved not only by RYGB-induced decreased CI and increased FO, but also via sympathetic nervous system activation, driven by increased peptide YY, CRF, and orexin signaling, decreasing FE and energy storage, demonstrated by reduced fat mass associated with the upregulation of mitochondrial uncoupling protein-2 in fat. These events override the compensatory response to the drop in leptin levels aimed at conserving energy.

Is a model useful in exploring the catabolic mechanisms of weight loss after gastric bypass in humans?

PURPOSE OF REVIEW

In the USA, approximately 3% of adults are morbidly obese, in whom behavior modification and drug therapy is ineffective in inducing major weight loss. Surgery is their only reliable option. The Roux-en-Y gastric bypass accounts for 90% of all bariatric surgeries because it achieves the best weight loss results. Many studies describe weight loss and changes in metabolic blood parameters after Roux-en-Y gastric bypass. We compare recent human data with the findings in our rats to validate the versatility of using a Roux-en-Y gastric bypass rat model to explore the multifactorial molecular and physiological dimensions of weight loss and weight regain.

RECENT FINDINGS

Not only mechanical factors but also changes in gastrointestinal and adipose hormones and hypothalamic neuropeptides contribute to Roux-en-Y gastric bypass induced weight loss by promoting catabolic processes. Nevertheless, the exact mechanisms of weight loss remain unknown.

SUMMARY

To investigate these catabolic mechanisms we used our Roux-en-Y gastric bypass rat model in diet induced obese rats. We found clear morphometric, physiological and biochemical parallelisms between humans and our rats. It is likely that Roux-en-Y gastric bypass induces similar changes in hypothalamic neuropeptides which can only be studied using the rat model. It therefore provides a useful research tool for exploring and studying the development of adjuvant antiobesity therapies.

The effect of insulin on cardiac autonomic balance predicts weight reduction after gastric bypass

AIMS/HYPOTHESIS

The aim of this study was to assess the predictive role of autonomic reactivity in body weight loss induced by gastric bypass.

METHODS

A group of 22 morbidly obese subjects, who were due to undergo a gastric bypass, were submitted, before surgery, to a euglycaemic-hyperinsulinaemic clamp, during which a continuous recording of the ECG was performed. The effect of insulin on cardiac autonomic balance was evaluated by performing power spectral analysis of heart rate variability. The low-to-high frequency ratio was calculated before and during the clamp and its modifications were expressed as % delta low-to-high frequency ratio (%Delta L: H).

RESULTS

Preoperative %Delta L: H showed a significant (p=0.0009, r2=0.43), positive relationship to the reduction of body weight, measured 1 year after surgery and expressed as % excess weight loss (% EWL). Preoperative BMI was also significantly (p=0.0009, r2=0.43) negatively related to the 12-month % EWL. In a multiple regression analysis, %Delta L: H remained a significant (p=0.003), independent predictor of body weight loss, even when preoperative BMI or age, % fat mass, insulinaemia and glucose disposal were taken into account.

CONCLUSIONS/INTERPRETATION

The best correction of excess body weight was achieved by those obese subjects who had a preserved capacity to shift their cardiac autonomic balance towards a sympathetic prevalence in response to an euglycaemic-hyperinsulinaemic clamp. Further studies are needed to elucidate the mechanisms through which the autonomic nervous system influences weight reduction.