Factors influencing long-term weight loss after bariatric surgery

Surgery for Obesity and Related Diseases 15 (2019) 456–461

Original article

Factors influencing long-term weight loss after bariatric surgery William W. Chang, M.D. a,∗, Devon N. Hawkins, M.D. a, Joel R. Brockmeyer, M.D. a, Byron J. Faler, M.D. a, Samuel W. Hoppe, M.D. a, Balakrishna M. Prasad, Ph.D. b a Department

of General Surgery, Dwight D. Eisenhower Army Medical Center, Fort Gordon, Georgia of Clinical Investigations, Dwight D. Eisenhower Army Medical Center, Fort Gordon, Georgia Received 26 September 2018; received in revised form 17 November 2018; accepted 24 December 2018

b Department

Abstract

Background: Bariatric surgery provides sustained weight loss and improves comorbidities. However, long term data has shown that patients gradually regain weight after 1 year. Several factors have been associated with poor weight loss after bariatric surgery. Objective: Our goal is to investigate factors associated with poor weight loss following laparoscopic sleeve gastrectomy (SG) and Roux-en-Y gastric bypass (RYGB). Setting: Military academic medical center. Methods: Retrospective review of 247 patients who underwent laparoscopic SG or RYGB between 2010–2012 at Eisenhower Army Medical Center and followed for 5 years postoperatively. Factors of age, type of surgery, sex, hypertension, depression, and type 2 diabetes (T2D) are analyzed in univariate and multivariate analysis with percent total weight loss (%TWL) and Body Mass Index (BMI) change as primary endpoints measured at 3 and 5 years. Results: Average BMI change are maximized at 1 year and decreased at 3 and 5 years postsurgery. Age, diabetes, hypertension and type of surgery significantly influenced weight loss at 3 and 5 years on univariate analysis. However, patients with diabetes, hypertension and sleeve gastrectomy were significantly older than comparable control group. Multivariable analysis showed that age and type of surgery, not diabetes or hypertension, were associated with poor %TWL and BMI change at 3 and 5 years. Conclusion: While presence of hypertension and diabetes initially appeared to be associated with weight recidivism, their impacts were negligible on multivariable analysis. However, age and sleeve gastrectomy are independent risk factors. Our data can be used to counsel patients on expected weight loss after bariatric surgery. (Surg Obes Relat Dis 2019;15:456–461.) Published by Elsevier Inc. on behalf of American Society for Bariatric Surgery.

Keywords:

Weight recividism; Bariatric surgery; Sleeve gastrectomy; Gastric bypass

Bariatric surgery is an effective treatment option to fight the increasing obesity epidemic and associated co-morbid conditions [1,2]. However, up to 15% of patients undergoing bariatric surgery may not achieve successful weight loss >50% excess weight [3,4]. Furthermore, maximal weight loss is observed at 1 to 2 years after surgery with weight regain after this initial postsurgical period [5]. ∗ Correspondence: William W. Chang, M.D., Dwight D. Eisenhower Army Medical Center, 300 E. Hospital Rd, Fort Gordon, GA 30905. E-mail address: [email protected] (W.W. Chang).

Multiple anthropometric, physiologic, and social factors have been implicated in poor weight loss or weight regain after bariatric surgery. For example, young age was reported to be associated with successful weight loss after Roux-en-Y gastric bypass (RYGB) in some [6,7], but not other, studies [8,9]. On the contrary, younger age was associated with weight regain after RYGB in another study [10]. Several factors, including small sample size, differences in the study design, and analysis methods, may have contributed to these disparate findings. Two studies using

https://doi.org/10.1016/j.soard.2018.12.033 1550-7289/Published by Elsevier Inc. on behalf of American Society for Bariatric Surgery.

William W. Chang, Devon N. Hawkins and Joel R. Brockmeyer et al. / Surgery for Obesity and Related Diseases 15 (2019) 456–461

multivariate analysis of data from the Bariatric Outcome Longitudinal Database (BOLD) demonstrated that younger age is associated with better weight loss. However, these 2 reports are based only on 1- to 2-year postsurgical data [11,12]. In an attempt to assess the relative roles of age and obesity associated co-morbidities in long-term weight loss, we performed a multivariable analysis of postsurgical weight change at our institute.

Methods Patient selection A retrospective review of all patients who underwent either RYGB or sleeve gastrectomy (SG) at Dwight D. Eisenhower Army Medical Center between the years 2010 and 2012 was conducted. Study protocol has been approved by the Dwight D. Eisenhower Army Medical Center local institutional review board. Weight data up to 5 postoperative years was collected and analyzed. Patients enrolled at the start of the bariatric pathway must have body mass index (BMI) of 35 kg/m2 with obesity-related co-morbidities or 40 kg/m2 without co-morbidities. All patients undergoing bariatric surgery at our institution are evaluated and counseled by psychiatrists or psychologists and nutritionists and must participate in bariatric support group meetings to proceed with surgery. Age, sex, type of surgery, pre- and postoperative anthropometric variables, and co-morbidities of type 2 diabetes (T2D), hypertension, and depression were analyzed. Patients with preoperative HbA1C >6.5% or those on diabetic medications are classified under T2D group. Therefore, patients with prediabetes were not included in the T2D group. In addition, patients are classified to be hypertensive, if they are on antihypertensive medication or if their presurgery systolic blood pressure is 140 mm Hg. Preoperative psychiatric evaluations and medication records were used to identify patients with depression. Primary endpoint was percent total weight loss (%TWL) and BMI change calculated by the equations below: Preoperative W eight − Current W eight x100 Preoperative W eight BMI change = Preoperative BMI − Current BMI %T W L =

Preoperative weight was obtained within 1 month of scheduled surgery date. BMI change and %TWL were measured at 2 weeks, 3 months, 6 months, 12 months, 3 years, and 5 years postoperatively. If a patient did not have follow-up weight or BMI recorded at the exact time point but had these values recorded within 1 month of the scheduled time point, that weight is used. All data points are presented as mean ± standard error of the mean.

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Ethical statement All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. Statistical analysis SAS 9.4 (SAS Analytics, Cary, NC, USA) was used for all statistical analyses. An alpha level of .05 was used to assess statistical significance. Descriptive statistics were calculated for all qualitative and quantitative variables. A 2-sample t test was performed to determine if type of surgery, hypertension, T2D, and depression groups were significantly different with respect to %TWL and BMI change at 3 and 5 years after surgery. In addition, Pearson’s correlation was calculated to examine associations between age at the time of surgery and weight at 3 and 5 years postsurgery. Multivariable analysis was performed separately for each outcome with age, type of surgery, T2D status, and hypertension status as independent variables. To determine the best model, all combinations of the independent variables were examined, and the coefficient of multiple determination (R2 ) for various reduced models was compared with the full (all variable) model. Also, the Akaike information criterion value was compared between the various model candidates. Results A total of 247 patients (23 males and 224 females) underwent RYGB or SG between the years of 2010 and 2012. The mean age was 44.7 ± 11.6 years (range, 19–72). The mean preoperative BMI and weights were 42.0 ± 5.7 and 253.6 ± 40.5 lbs, respectively. All other patient demographic characteristics are noted in Table 1. There was 1 laparoscopic converted to open RYGB that was included in the laparoscopic RYGB group. Pearson’s correlation analysis showed that age at the time of surgery had a significant negative correlation with BMI change and %TWL at 3 and 5 years after surgery (BMI: 3 years r = −.382, 5 years r = −.316; %TWL: 3 years r = −.388, 5 years r = −.329; P < .0001 for all 4 values). Univariate analyses were conducted to investigate the role of hypertension, T2D, depression, and type of surgery on BMI change and %TWL at 3 and 5 years after surgery. When comparing patients with and without hypertension, a statistically significant difference for BMI change (P = .016 and .039) and %TWL (P = .005 and .017) at 3 and 5 years, respectively (Fig. 1). However, the group with hypertension were older (50.4 ± 9.6 versus 37.9 ± 9.9 yr, P < .0001). When comparing patients with and without T2D, there

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Table 1 Baseline Characteristics of Study Patients. Variables

N

Mean

SD

Minimum

Maximum

Age Preoperative BMI Preoperative Weight Hypertension Yes No Sex Male Female T2D Yes No Depression Yes No Surgery Type Laparoscopic RYGB Laparoscopic SG Open RYGB

247 247 247 N 134 113

44.65 41.98 253.6 Percent 54.25 45.75

11.55 5.71 40.47

19 31.55 176.8

72 75.69 426.4

23 224

9.31 90.69

48 199

19.4 80.6

47 200

19 81

36 210 1

14.57 85.02 0.4

SD = standard deviation; BMI = body mass index; T2D = type 2 diabetes; RYGB = Roux-en-Y gastric bypass; SG = sleeve gastrectomy. A total of 247 patients are included in this study. The number of patients with different co-morbidities and type of surgery performed are shown.

Fig. 1. Effect of preoperative hypertension on weight loss after bariatric surgery. Change in body mass index (A) and percent of total weight lost (B) in patients with (HTN) or without hypertension (No HTN) are shown as mean ± standard error of the mean. P values corresponding to significant differences between 2 groups are shown. N values at different time points are 2 weeks – HTN: 74, No HTN: 61; 3 months – HTN: 98, No HTN: 77; 6 months – HTN: 98, No HTN: 78; 12 months – HTN: 108, No HTN: 85; 3 years – HTN: 104, No HTN: 69 and 5 years – HTN: 95, No HTN: 59.

was a statistically significant difference between patients with and without T2D at 3 years in terms of BMI change and %TWL (P = .011). At 5 years, it was approaching statistical significance in terms of BMI change and %TWL (P = .058 and .076, respectively) (Fig. 2). Similar to hyper-

Fig. 2. Effect of preoperative type 2 diabetes (T2D) on weight loss after bariatric surgery. Change in body mass index (A) and percent of total weight lost (B) in patients with T2D or no T2D are shown as mean ± standard error of the mean. P values corresponding to significant differences between 2 groups are shown. N values at different time points are 2 weeks – T2D 24, No T2D: 111; 3 months – T2D: 35, No T2D: 141; 6 months – T2D:38, No T2D: 137; 12 months – T2D: 40, No T2D: 152; 3 years – T2D: 33, No T2D: 140; and 5 years – T2D: 35, No T2D: 119.

tension group, patients with T2D were also older (52.3 ± 9.8 versus 42.9 ± 11.3, P < .0001). For depression, there was no statistical significance between the 2 groups at any time point (Fig. 3). When analyzing type of surgery, the RYGB group had more BMI change (13.3 ± 5.9 at 3 yr, 13.0 ± 5.1 at 5 yr) and %TWL (31.9 ± 13.45 at 3 yr, 31.0 ± 11.3 at 5 yr) (Fig. 4). However, the mean age of patients in the RYGB group was lower than those of SG group (39.6 ± 11.6 versus 45.5 ± 11.3). Because hypertension, T2D, surgery type, and age were individually found to be significantly associated with the primary endpoint at 3 and 5 years postoperatively, these variables were examined together in a multivariable analysis. This analysis showed that age and type of surgery were independent predictors of weight loss at 3 and 5 years. After controlling for age and surgery type, the presence of T2D and hypertension were no longer statistically significant in terms of BMI change and %TWL (Table 2). Analysis of covariance illustrates that age is negatively correlated with BMI change and RYGB has better weight loss at 3 and 5 years (Fig. 5). Discussion The main findings of our retrospective analysis are that young age at the time of surgery and those undergoing RYGB are more likely to have better weight control up to 5

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Table 2 Multivariable analysis of weight loss data. Outcome

Source

P value

R²

BMI change (3 yr)

Age Surgery type Hypertension T2D Age Surgery type Hypertension T2D Age Surgery type Hypertension T2D Age Surgery type Hypertension T2D

<.0001 .0087 .6434 .1871 .0047 .0051 .8361 .4292 .0001 .0034 .9752 .2082 .0042 .0028 .9274 .5579

17.5%

BMI change (5 yr)

%TWL loss (3 yr)

%TWL loss (5 yr)

14.6%

18.9%

16.0%

BMI = body mass index; T2D = type 2 diabetes; %TWL = percent total weight loss. Significant effect of different parameters and corresponding P and R2 values are shown. Fig. 3. Effect of preoperative depression on weight loss after bariatric surgery. Change in body mass index (A) and percent of total weight lost (B) in patients with or without depression are shown as mean ± standard error of the mean. P values corresponding to significant differences between 2 groups are shown. N values at different time points are 2 weeks – Depression: 32, No Depression: 103; 3 months – Depression: 33, No Depression: 143; 6 months – Depression: 34, No Depression: 141; 12 months – Depression: 36, No Depression: 156; 3 years – Depression: 31, No Depression: 142 and 5 years – Depression: 25, No Depression: 129.

Fig. 4. Effect of type of surgery on weight loss after bariatric surgery. Change in body mass index (A) and percent of total weight lost (B) at different time points after bariatric surgery are shown as mean ± standard error of the mean. P values corresponding to significant differences between type of surgery (sleeve gastrectomy [SG] versus Roux-en-Y gastric bypass [RYGB]) are shown. N values at different time points are 2 weeks – SG: 115, RYGB: 20; 3 months – SG: 151, RYGB: 25; 6 months – SG: 148, RYGB: 27; 12 months – SG: 164, RYGB: 28; 3 years – SG: 151, RYGB: 22 and 5 years – SG: 137, RYGB: 17.

years after surgery. While T2D and hypertension appeared to be risk factors for poor weight loss, their association with BMI change was not truly independent and was most likely related to age. These findings add to the growing number of studies showing a relationship between age and weight loss after bariatric surgery. Some of the contradictory reports on the relationship between age and postoperative weight loss/regain are based on small sample size and univariate analysis [6–10]. These studies used successful weight loss (defined as >50% excess weight) as a criterion to classify study patients into 2 groups. Statistical analysis of age, co-morbidity prevalence, and other variables in these 2 groups were used to determine the role of each factor. However, the binary classification of continuous variable (weight parameters) and small sample size are likely to lead to erroneous conclusions and may be responsible for the contrasting findings on the role of age and co-morbidities. Multivariable analysis of large data sets (from BOLD database) show that age is indeed inversely correlated to weight loss at 1 to 2 years after surgery [11,12]. We reconfirm these observations and further extend them to 3- and 5-year postsurgical periods. Among the different postsurgical time points analyzed in our study, maximal weight loss occurred at 1 year, similar to the time frame reported in large scale prospective studies [5,13]. Some weight regain occurred at 3 and 5 years, especially in SG patients. This trend was also observed in a large long-term retrospective analysis of SG patients where the %TWL was 33.4% at 1 year, and 27.9 and 28.3% at 3 and 5 years, respectively [13]. Although the effects of age were statistically significant in the 6-month and 1-year postsurgical periods in correlation analyses, we decided to use 3- and 5-year data for multivariable analysis to assess

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Fig. 5. Analysis of covariance between age and weight loss after surgery. Change in body mass index at 3 years (A) and 5 years (B) for all patients are plotted in relationship to their age. Data points for Roux-en-Y gastric bypass (blue) and sleeve gastrectomy (red) and their corresponding regression lines are shown. Best-fit regression equation for 3-year data is BMI change = 17.46 – .16 × age + 2.59 × surgery type∗ , while that for 5-year data is body mass index change = 15.05 – .14 × age + 3.61 × surgery type∗ . ∗ value for surgery type is 0 for SG and 1 for RYGB.

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the effect on long-term weight loss, which includes weight regain period. Limitations of our study include its retrospective nature, data obtained from single institution, and small sample size compared with BOLD-based studies. Another limitation is loss of observations at follow-up points, especially at 5 years. It is possible that the differential follow-up rates (65% for SG and 46% for RYGB at 5 years) is responsible for the observed differences in weight due to type of surgery. However, this is unlikely as the loss to follow-up is not necessarily caused by noncompliance due to poor weight loss. Furthermore, because of uniform electronic medical records in the military system, we were able to get better long-term follow-up rates than published reports on bariatric surgery [9,10]. Although, we show that age at surgery and type of surgery are certainly associated with postsurgical weight loss, it is difficult to predict weight loss using these 2 parameters as the regression coefficient was small (Fig. 5). Approximately 17.5% and 14.6% of variability in BMI change in our data set at 3 and 5 years, respectively, can be explained by the combined effect of age and surgery type (Table 2). Only <1% of variability in weight loss was reported to be associated with age in a BOLD-based study [11]. Time after surgery and other patient-related factors might be responsible for relative magnitude of effect of age in different studies. However, our data add to the developing consensus that younger age at surgery is a favorable factor for successful long-term weight loss. Future large scale studies with longer postsurgical follow-up periods might enable us to better understand the factors associated with successful weight loss. Furthermore, the metabolic pathways and biomarkers associated with successful weight loss is an open area for fruitful future research. Conclusion Our data presented here can be used for patient counseling, however, additional long-term data are needed to change clinical practice of bariatric procedures. Even with poor weight loss, older patients are still likely to benefit from bariatric surgery, especially from improvement in co-morbid conditions. Furthermore, our data show that SG may offer less advantage in terms of long-term weight loss compared with RYGB even though the amount of weight loss was equivalent up to 1 year postoperatively. More long-term follow-up studies comparing SG with RYGB in terms of weight recidivism are needed to further elucidate this effect. Our data can be used to provide informed

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counseling about expected long-term weight loss for patients scheduled for bariatric surgery. Disclosures The authors have no commercial associations that might be a conflict of interest in relation to this article. The opinions or assertions in this article are those of the authors and are not to be construed as official or reflecting the views and opinions of the Army, the Department of Defense, or the United States Government. References [1] Sjöström L. Review of the key results from the Swedish Obese Patients (SOS) trial - a prospective controlled intervention study of bariatric surgery. J Intern Med 2013;273(3):219–34. [2] Müller-Stich BP, Senft JD, Warschkow R, et al. Surgical versus medical treatment of type 2 diabetes mellitus in nonseverely obese patients: a systematic review and meta-analysis. Ann Surg 2015;261(3):421–9. [3] Salem L, Jensen CC, Flum DR. Are bariatric surgical outcomes worth their cost? A systematic review. J Am Coll Surg 2005;200(2):270–8. [4] Christou NV, Look D, MacLean LD. Weight gain after short- and long-limb gastric bypass in patients followed for longer than 10 years. Ann Surg 2006;244(5):734–40. [5] Sjostrom L, Narbro K, Sjostrom CD, et al. Effects of bariatric surgery on mortality in Swedish obese patients. N Engl J Med 2017;357(8):741–52. [6] Ma Y, Pagoto SL, Olendzki BC, et al. Predictors of weight status following laparoscopic gastric bypass. Obes Surg 2006; 16(9):1227–31. [7] Contreras JE, Santander C, Court I, Bravo J. Correlation between age and weight loss after bariatric surgery. Obes Surg 2013; 23(8):1286–9. [8] Campos GM, Rabl C, Mulligan K, et al. Factors associated with weight loss after gastric bypass. Arch Surg 2008;143(9):877–83. [9] Júnior WS, do Amaral JL, Nonino-Borges CB. Factors related to weight loss up to 4 years after bariatric surgery. Obes Surg 2011;21(11):1724–30. [10] Shantavasinkul PC, Omotosho P, Corsino L, Portenier D, Torquati A. Predictors of weight regain in patients who underwent Roux-en-Y gastric bypass surgery. Surg Obes Relat Dis 2016;12(9):1640–5. [11] Benoit SC, Hunter TD, Francis DM, De La Cruz-Munoz N. Use of bariatric outcomes longitudinal database (BOLD) to study variability in patient success after bariatric surgery. Obes Surg 2014; 24(6):936–43. [12] Van de Laar AW. Algorithm for weight loss after gastric bypass surgery considering body mass index, gender, and age from the Bariatric Outcome Longitudinal Database (BOLD). Surg Obes Relat Dis 2014;10(1):55–61. [13] Chang DM, Lee WJ, Chen JC, Ser KH, Tsao PL, Lee YC. Thirteen-year experience of laparoscopic sleeve gastrectomy: surgical risk, weight loss and revision procedures. Obes Surg. Epub 2018 Jun 21.