OBES SURG (2014) 24:727–734 DOI 10.1007/s11695-013-1130-9
ORIGINAL CONTRIBUTIONS
Weight Loss Percentile Charts of Large Representative Series: a Benchmark Defining Sufficient Weight Loss Challenging Current Criteria for Success of Bariatric Surgery Arnold W. J. M. van de Laar & Yair I. Z. Acherman
Published online: 14 November 2013 # Springer Science+Business Media New York 2013
Abstract Background The frequently used 35 kg/m2 body mass index (BMI) and 50 % excess weight loss (%EWL) criteria are no longer adequate for defining the success of a bariatric or metabolic surgery. It is not clear whether they are still useful to simply determine the sufficiency of a patient’s postoperative weight loss. An alternative way of defining sufficient weight loss is presented, using weight loss percentile charts of large representative series as a benchmark. Methods Gastric bypass weight loss results from the Bariatric Outcomes Longitudinal Database (BOLD) with ≥2 years of follow-up are presented with percentiles in function of postoperative time and their nadir results in function of initial BMI using different outcome metrics. These percentiles are compared with the BMI35 and 50 %EWL criteria. Results Of 49,098 patients eligible for ≥2 years of follow-up, 8,945 had reported weight loss at ≥2 years (20.0 % male, mean initial BMI 47.7 kg/m2). They reached nadir BMI at a mean of 603 days. Their 50th percentiles surpassed both 50 %EWL and BMI35 after 135 days. More than 95 % achieved 50 %EWL; more than 75 % achieved BMI35. BMI and %EWL results are influenced more by initial BMI than total weight loss (%TWL) results. Conclusions BOLD gastric bypass weight loss data are presented with percentile curves. BMI and %EWL are clearly not suited for this purpose. Provided that follow-up data are solid, %TWL-based percentile charts can constitute neutral benchmarks for defining sufficient postoperative weight loss over time. Criteria for overall success, however, should consider A. W. J. M. van de Laar (*) : Y. I. Z. Acherman Bariatric Surgery, Slotervaartziekenhuis, Louwesweg 6, Amsterdam 1066EC, The Netherlands e-mail: [email protected] Y. I. Z. Acherman e-mail: [email protected]
clear goals of health improvement, including metabolic aspects. Frequently used criteria 50 %EWL and BMI35 are inadequate for both. Their static weight loss components do not match the found percentiles and their health improvement components do not match known metabolic criteria. Keywords BOLD . Database . Weight loss . Bariatric surgery . Success criteria . LRYGB . Weight loss results . Percentile chart
Introduction In surgery, the benefit of an operation should outweigh the risk involved. In bariatric surgery, in particular, insights in both benefit and risk have evolved tremendously in recent years. It is now well established that it does not only offer sustainable weight loss but can improve both long-term mortality and metabolic impairment as well, while perioperative mortality dropped from 1 % in 1987 to 0.13 % in 2010 [1–5]. The definition of success of this type of surgery should therefore be adjusted accordingly as old bariatric criteria are still in use. In 1981, Reinhold first defined success of bariatric surgery based on this risk–benefit principle [6]. He used the then known correlation between absolute body weight and general health and expressed postoperative weight as multiples of the patient’s ideal body weight (IBW), labeling 200 %IBW failure, 150 %IBW success, and 125 %IBW excellent. MacLean et al. modified the Reinhold classification in 1993, converting the cumbersome multiples of IBW into body mass index (BMI) criteria: BMI35 for success and BMI30 for excellent result [7]. However, the most widespread used definitions of bariatric failure and success became the 25 % and 50 % excess weight loss (%EWL) marks (often mistaken for the Reinhold criteria). They were introduced by Oria in 1998 as part of an elaborate scoring system [8], but as single weight loss
728
thresholds, they had no evidence-based correlation with either benefit or risk. These BMI35 and 50 %EWL marks are still used as bariatric weight loss criteria, implying a certain level of successful overall health improvement. However, now that metabolic benefits of bariatric surgery are recognized, bariatric success should be redefined, above all, by metabolic criteria. There are several definitions of the metabolic syndrome in use at present with more or less similar criteria for glucose intolerance, hypertension, dyslipidemia, and overweight. In none of them, however, EWL, IBW, or BMI is considered as measure for overweight. They all use waist circumference or hip–waist ratio instead [9–13]. The BMI35 and 50 %EWL criteria are therefore no longer adequate for defining success of bariatric surgery. Whether they are still useful to simply determine the sufficiency of a patient’s weight loss after bariatric surgery is the first question we try to answer in this article. The second aim of this study is to find out how an alternative for these weight loss criteria should look like. Above all, sufficiency of individual weight loss after bariatric surgery should be looked at separately from the overall success. Indeed patients with disappointing weight loss might have great metabolic improvement, while others with satisfying weight loss might have none. Metabolic success can be determined by means of the evidence-based criteria of the metabolic syndrome. The sufficiency of postoperative weight loss can be determined in two ways: first, individual weight loss can be compared with a preset goal, like the BMI35 or 50 %EWL criteria are being used, as fixed landmarks set by consensus; second, individual weight loss can be compared with the weight loss results of many other patients that underwent the same procedure, serving as a benchmark. Postoperative weight loss results in large series show distinct deviation: most patients do average, some do better or worse, and a few do excellent or bad. Results can thus be divided into groups using percentiles. A percentile chart of weight loss results of large representative series can then be used as a tool to determine the sufficiency of an individual weight loss result, similar to the use of children’s growth charts, for example. A major advantage of a percentile-based benchmark is that it considers the dynamics of postoperative weight loss, known to show a high speed in the first year and weight regain in later years. Therefore, percentile charts should be based on large numbers of patients from multiple surgeons and centers with essentially solid midterm follow-up data. Another advantage of weight loss percentile charts is that they are neutral, not at all implying whether a certain amount of weight loss is good or bad for a patient’s health. Finally, different charts can be made according to basic patient characteristics like gender, age, or baseline BMI. Percentile information in bariatric literature however is scarce and usually limited to 25 %EWL and 50 %EWL outcome.
OBES SURG (2014) 24:727–734
Materials and Methods Data from the largest available database of bariatric weight loss results at present, the multicenter Bariatric Outcomes Longitudinal Database (BOLD), are used to build an example of dynamic percentile weight loss charts. Those charts are then compared with the static criteria 50 %EWL and BMI35. The Institutional Review Board approved the present study. The September 2011 BOLD database cut was searched for all patients that underwent a primary fully laparoscopic Rouxen-Y gastric bypass, with a reported postoperative follow-up of at least 2 years and with initial BMI at first preoperative visit between 30 and 80 kg/m2. The BMI at first preoperative visit and at every reported postoperative visit of all these patients are collected and analyzed for the whole group, differentiated by gender, and for the morbid obese (MO, initial BMI
ORIGINAL CONTRIBUTIONS
Weight Loss Percentile Charts of Large Representative Series: a Benchmark Defining Sufficient Weight Loss Challenging Current Criteria for Success of Bariatric Surgery Arnold W. J. M. van de Laar & Yair I. Z. Acherman
Published online: 14 November 2013 # Springer Science+Business Media New York 2013
Abstract Background The frequently used 35 kg/m2 body mass index (BMI) and 50 % excess weight loss (%EWL) criteria are no longer adequate for defining the success of a bariatric or metabolic surgery. It is not clear whether they are still useful to simply determine the sufficiency of a patient’s postoperative weight loss. An alternative way of defining sufficient weight loss is presented, using weight loss percentile charts of large representative series as a benchmark. Methods Gastric bypass weight loss results from the Bariatric Outcomes Longitudinal Database (BOLD) with ≥2 years of follow-up are presented with percentiles in function of postoperative time and their nadir results in function of initial BMI using different outcome metrics. These percentiles are compared with the BMI35 and 50 %EWL criteria. Results Of 49,098 patients eligible for ≥2 years of follow-up, 8,945 had reported weight loss at ≥2 years (20.0 % male, mean initial BMI 47.7 kg/m2). They reached nadir BMI at a mean of 603 days. Their 50th percentiles surpassed both 50 %EWL and BMI35 after 135 days. More than 95 % achieved 50 %EWL; more than 75 % achieved BMI35. BMI and %EWL results are influenced more by initial BMI than total weight loss (%TWL) results. Conclusions BOLD gastric bypass weight loss data are presented with percentile curves. BMI and %EWL are clearly not suited for this purpose. Provided that follow-up data are solid, %TWL-based percentile charts can constitute neutral benchmarks for defining sufficient postoperative weight loss over time. Criteria for overall success, however, should consider A. W. J. M. van de Laar (*) : Y. I. Z. Acherman Bariatric Surgery, Slotervaartziekenhuis, Louwesweg 6, Amsterdam 1066EC, The Netherlands e-mail: [email protected] Y. I. Z. Acherman e-mail: [email protected]
clear goals of health improvement, including metabolic aspects. Frequently used criteria 50 %EWL and BMI35 are inadequate for both. Their static weight loss components do not match the found percentiles and their health improvement components do not match known metabolic criteria. Keywords BOLD . Database . Weight loss . Bariatric surgery . Success criteria . LRYGB . Weight loss results . Percentile chart
Introduction In surgery, the benefit of an operation should outweigh the risk involved. In bariatric surgery, in particular, insights in both benefit and risk have evolved tremendously in recent years. It is now well established that it does not only offer sustainable weight loss but can improve both long-term mortality and metabolic impairment as well, while perioperative mortality dropped from 1 % in 1987 to 0.13 % in 2010 [1–5]. The definition of success of this type of surgery should therefore be adjusted accordingly as old bariatric criteria are still in use. In 1981, Reinhold first defined success of bariatric surgery based on this risk–benefit principle [6]. He used the then known correlation between absolute body weight and general health and expressed postoperative weight as multiples of the patient’s ideal body weight (IBW), labeling 200 %IBW failure, 150 %IBW success, and 125 %IBW excellent. MacLean et al. modified the Reinhold classification in 1993, converting the cumbersome multiples of IBW into body mass index (BMI) criteria: BMI35 for success and BMI30 for excellent result [7]. However, the most widespread used definitions of bariatric failure and success became the 25 % and 50 % excess weight loss (%EWL) marks (often mistaken for the Reinhold criteria). They were introduced by Oria in 1998 as part of an elaborate scoring system [8], but as single weight loss
728
thresholds, they had no evidence-based correlation with either benefit or risk. These BMI35 and 50 %EWL marks are still used as bariatric weight loss criteria, implying a certain level of successful overall health improvement. However, now that metabolic benefits of bariatric surgery are recognized, bariatric success should be redefined, above all, by metabolic criteria. There are several definitions of the metabolic syndrome in use at present with more or less similar criteria for glucose intolerance, hypertension, dyslipidemia, and overweight. In none of them, however, EWL, IBW, or BMI is considered as measure for overweight. They all use waist circumference or hip–waist ratio instead [9–13]. The BMI35 and 50 %EWL criteria are therefore no longer adequate for defining success of bariatric surgery. Whether they are still useful to simply determine the sufficiency of a patient’s weight loss after bariatric surgery is the first question we try to answer in this article. The second aim of this study is to find out how an alternative for these weight loss criteria should look like. Above all, sufficiency of individual weight loss after bariatric surgery should be looked at separately from the overall success. Indeed patients with disappointing weight loss might have great metabolic improvement, while others with satisfying weight loss might have none. Metabolic success can be determined by means of the evidence-based criteria of the metabolic syndrome. The sufficiency of postoperative weight loss can be determined in two ways: first, individual weight loss can be compared with a preset goal, like the BMI35 or 50 %EWL criteria are being used, as fixed landmarks set by consensus; second, individual weight loss can be compared with the weight loss results of many other patients that underwent the same procedure, serving as a benchmark. Postoperative weight loss results in large series show distinct deviation: most patients do average, some do better or worse, and a few do excellent or bad. Results can thus be divided into groups using percentiles. A percentile chart of weight loss results of large representative series can then be used as a tool to determine the sufficiency of an individual weight loss result, similar to the use of children’s growth charts, for example. A major advantage of a percentile-based benchmark is that it considers the dynamics of postoperative weight loss, known to show a high speed in the first year and weight regain in later years. Therefore, percentile charts should be based on large numbers of patients from multiple surgeons and centers with essentially solid midterm follow-up data. Another advantage of weight loss percentile charts is that they are neutral, not at all implying whether a certain amount of weight loss is good or bad for a patient’s health. Finally, different charts can be made according to basic patient characteristics like gender, age, or baseline BMI. Percentile information in bariatric literature however is scarce and usually limited to 25 %EWL and 50 %EWL outcome.
OBES SURG (2014) 24:727–734
Materials and Methods Data from the largest available database of bariatric weight loss results at present, the multicenter Bariatric Outcomes Longitudinal Database (BOLD), are used to build an example of dynamic percentile weight loss charts. Those charts are then compared with the static criteria 50 %EWL and BMI35. The Institutional Review Board approved the present study. The September 2011 BOLD database cut was searched for all patients that underwent a primary fully laparoscopic Rouxen-Y gastric bypass, with a reported postoperative follow-up of at least 2 years and with initial BMI at first preoperative visit between 30 and 80 kg/m2. The BMI at first preoperative visit and at every reported postoperative visit of all these patients are collected and analyzed for the whole group, differentiated by gender, and for the morbid obese (MO, initial BMI
