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Journal of Obesity
Volume 2012, Article ID 867540, 7 pages
doi:10.1155/2012/867540
Review A rticle
The Effect of Preoperative Weight Loss before Gastric Bypass:
ASystematicReview
Deepak K. Kadeli,
1
John P. Sczepaniak,
1, 2
Kavita Kumar,
1
Christie Youssef,
1
Arash Mahdavi,
2
and Milton Owens
2
1
John Sczepaniak Medical Enter prises, 6871 Eberhart Street, San Diego, CA 92115, USA
2
Coastal Center for Obesity, 2617 East Chapman Avenue, Suite 307, Orange, CA 92869, USA
Correspondence should be addressed to Deepak K. Kadeli, kadelideepak@gmail.com
Received 1 November 2011; Accepted 10 April 2012
Academic Editor: Natan Zundel
Copyright © 2012 Deepak K. Kadeli et al. This is an open access article distributed under the Creative Commons Attribution
License, which permits unrestricted use, distribution, and reproduction i n any medium, provided the original work is properly
cited.
Background. Many insurance companies require obese patients to lose weight prior to gastric bypass. From a previous study by the
same authors, preoperative weight at surgery is strongly predictive of weight loss up to one year after surgery. T his review aims to
determine whether preoperative weight loss is also correlated with weight loss up to one year after surgery. Methods. Of the 186
results screened using PubMed, 12 studies were identified. A meta-analysis was performed to further classify studies (A class, B
class, regression, and rejected). Results. Of all 12 studies, one met the criteria for A class, six were B class, four were regression,
and one was rejected. Six studies supported our hypothesis, five were inconclusive, and no study refuted. Conclusions.Preoperative
weight loss is additive to postsurgery weight loss as predicted from the weight at the time of surgery.
1. Introduction
According to the latest statistics, one out of every three
adults (33.8%) in US is obese. Additionally, the rate of
morbid obesity is 5.7% in adults [1]. Bariatric surgery is
averyeffective intervention for the morbidly obese. More
than 220,000 people underwent some form of bariatric
surgery in 2008 [2]. Age, gender, race, height, initial body
weight, postoperative behaviors, type of operation, and
surgeon have been reported to affect weight loss following
surgery. However, no consideration of factors impacting
weight loss outcomes would be complete without attention
to the importance of preoperative weight loss. Although
the California Department of Managed Care explicitly states
that “there is no literature presented by any authority that
mandated weight loss, once a patient has been identified
as a candidate for bariatric surgery, is indicated,” yet the
majority of insurance payers continue to require prolonged
dietar y efforts as a prerequisite to surgical treatment [3].
A reduction in the size of the liver after four weeks of
dieting and an increase in ease of surgical exposure are well
documented [4, 5]. The impact on overall weight loss is less
clear. Numerous papers dealing with the subject provide an
array of experimental models that make a comparison of
results difficult. Our paper evaluates the existing publications
and separates them into four groups for comparison.
In a previous publication, we showed that weight loss in
the first year after gastric bypass is a p ercent of initial body
weight [6]. The following review attempts to determine the
effect of short-term preoperative weight loss on weight loss
following surgery and the effect of initial body weig ht.
2. Methods
The study was done using PubMed search for those papers
which dealt with aspects of preoperative weight loss before
bariatric surgery. The search terms used were (“preoperative
weight loss” or “pre-operative weight loss” or “preoperative
weight”or“pre-operativeweight”)and(“gastricbypass”
(meSH) or “bariatric surgery” (meSH) or “obesity surgery”
or “weight reduction surgery” or “predicting”).
Each abstract was analyzed to include only those studies
which satisfied all set criteria. Criteria for abst ract review
2 Journal of Obesity
were as follows. All studies reviewed were from a peer-
reviewed source and published either in English or Span-
ish. Studies were required to have one of the following
designs: randomized control trials, case control studies, or
series/cohort studies. Additionally, the majority of study
participants had to be greater than 18 years old. Accepted
abstracts included both open and laparoscopic cases.
Articles were obtained for the remaining abstracts and
were further analyzed. Each article was expected to have
more than ten patients in each group of study (preoperative
weight loss versus weight gain) or >20 patients in a regression
analysis. Information on pre/post-operation weight loss had
to be available for article selection. Papers were also excluded
that did not stratify the data such that gastric bypass
weight loss results were separated from alternate weight loss
procedures such as gastric banding or sleeve gastrectomy
(Figure 1). The selected studies were further searched for
their references to identify more papers pertaining to our
study.
The selected studies were divided into different classes:
class A, class B, and regression studies. The classification was
based on the patient’s weight at initial consultation and the
weight at surgery. Both class A and class B studies grouped
patients into two follow-up cohorts, one that lost weight and
the other that did not.
In class A studies, the weight loss and weight gain
groups both had the same mean weight at initial consultation
but different at the time they went for surgery. This is
demonstrated in Figure 2 by using two groups with five
hypothetical patients in each group. Both groups initially
begin with similar mean weights and differ directly prior to
surgery with different average weights (confidence interval
95%).
2.1. Class A Study Supporting/Refuting Criteria. Studies were
deemed to support our hypothesis if both groups of patients
had a persistent statistical difference in the average weight
within the first 12 months, and the mean weight values did
not crossover in this time fr a me. Refuting studies would
have crossing over of the means (e.g., the weight loss group
having a higher mean weight after surgery at six months
than the weight gain group). Inconclusive studies lacked 50%
followup during the first year or proper notation to elicit a
definitive conclusion.
In class B studies weight loss and weight gain groups had
different mean weights (P<0.05) at initial consultation but
similar means at the time of surgery. This is demonstrated
in Figure 3 by using two groups with five hypothetical
patients in each who begin with different weights at initial
consultation but eventually enter the surgery with similar
mean weights.
2.2. Class B Study Supporting/Refuting Criteria. Studies were
deemed to support our hypothesis if both groups of patients
did not have any statistical difference in their mean weight for
the first 12 months. Refuting studies would have a statistically
different differences between the weight loss and weight gain
group. Inconclusive studies lacked 50% followup during the
first year or proper notation to elicit a definitive conclusion.
2.3. Regression Studies. Regression studies do not have to
utilize groups of patients and may look at preoperative
weight loss as a variable. In regression studies the patients
are no longer grouped into weight loss/gain groups or
dieters/nondieters g roups. The focus is on individual per-
formance of each patient. The following concept has been
explained by using six hypothetical patients who undergo
gastric bypass surgery (P1, P2, P3, P4, P5, and P6). Each
of these hypothetical patients had different amounts of
preoperative weight loss with the exception of one patient
who did not lose or gain weight.
Thepreoperativeweightlossisconsideredtobeacon-
tinuous variable and can be plotted on the x-axis (Figure 4).
The outcome is also a continuous variable percent of initial
weight loss, plotted on y-axis (Figure 5)foraperiodofone
year after surgery. For explanation and standardization, we
use percent of initial weight at surgery as the outcome for
y-axis.
2.4. Regression Study Supporting/Refuting Criteria. Regres-
sion studies were judged based on the variables included and
the results reported by the authors. Analysis was hampered
due to absence of data or modeling protocol. Inconclusive
studies were defined as <50% followup or too complex for us
to interpret without additional input from the author.
Classification of studies was required to define criteria
needed to support and refute our hypothesis.
A flow chart used to arrive at the chosen classification is
provided in Figure 5.
3. Results
3.1. Class A Studies. The study by Solomon et al. [7]and
Alami et al. [19] was a randomized control trial conducted
at Stanford Medical University. The study was done for a
year comparing postoperative weights between two groups,
one which lost weight preoperatively and other which gained
weight. The statistical difference between both groups was
maintained up to 3 months. At one year, the patients in
both arms of the study showed no difference in excess weight
loss. But when patients were divided according to those who
had lost at least five percent of their excess body weight
preoperatively, the one-year results for excess weight loss
were much lower for the weight-loss group. This class-A
study shows that weight loss is a percent of initial b ody
weight at the time of surgery (Table 1).
3.2. Class B Studies. In the study by Martin e t al. [8], the
subjects were divided into dieters and nondieters. Here,
also the data show that weight loss after surgery is a
percent of body weight at the time of surgery. The only
statistically significant difference in mean weight between
the two groups was at initial presentation (Tab le 2 ). The
studybyStilletal.[9] was done at Geisinger Medical
Center in Danville, Pennsylvania. This study was considered
Journal of Obesity 3
MeSH results in Pubmed search for preoperative
122 search results were further
reviewed for the criteria
46 full text articles
were analyzed
12 were
chosen
76 abstracts were excluded as they did not
meet one of the above criteria
34 articles were excluded as they did not fulfill
added requirements
weight loss—186 titles and abstracts found
64 abstracts excluded—unrelated topics
Figure 1: Diagram representing the inclusion and exclusion of PubMed search results.
Table 1: Class A studies.
Lead author Study design Group Patients Mean age (yr) Female (%) Results
Solomon [7]
RCT
WL 26 42.4 88.5%
Supportive
WG 35 44.9 80.0%
WL: weight loss; WG: weight gain; RCT: randomized controlled trial.
Mean
∗
Mean
Mean
∗
Mean
Initial weight at consultation Initial weight at surgery
Weight (kilograms)/BMI/percent excess weight
Figure 2: Example of Class A study. Graph showing ten hypothet-
ical patients in Class A study that have been divided into weight
loss (blue) and weight gain (red) groups. The weight loss group
was statistically different from the weight gain g roup at surgery.
∗
Confidence Interval 95%.
inconclusive because its postoperative assessment was carried
out in percentages of patients meeting their weight loss goal
as opposed to actual weight values making analysis difficult.
Ali et al. [10] had 351 subjects who were divided into 4
groups based on the percent EWL (excess weight loss). At
surgery, no significant differences were found among the 4
groups in total body weight and BMI or EBW except for a
BMI difference in group 1 and 3. At 6 and 12 months, no
significant difference was found in the total body weight or
Mean
∗
Mean
Mean
∗
Mean
Initial weight at consultaion Initial weight at surgery
Weight (kilograms)/BMI/percent excess weight
Figure 3: Example of class B study. Graph showing ten hypothetical
patients in class B study who have been divided into weight
loss (blue) and weight gain (red) groups. The weight loss group
was statistically different from the weight gain group at initial
consultation.
∗
Confidence interval 95%.
BMI among the 4 groups indicating again that weight loss is
a function of weight at the time of surgery (Ta bl e 2).
The study by Fujioka et al. [11] divided the patients
into two groups based on whether patients lost or gained
weight preoperatively. Both groups had similar mean weights
at surgery. When these patients were followed after surgery,
no significant differences in the mean EWL were found at
any follow-up point in the first 12 months thus supporting
our hypothesis. Harnish’s et al. [12] study also had similar
structure and findings to that of Fujioka (Table 2 ).
4 Journal of Obesity
Table 2: Class B studies.
Lead author Study design Group Patients Mean age Female (%) Results
Martin [8]
Prospective
WL (dieters) 47 40.2 74.5%
Supportive
WG (nondiet) 53 38.8 92.5%
Still [9]
Prospective
5–10% EBWL 67 43 77.6%
Inconclusive
5% EBWL 86 43 74.4%
0–5% EBWG 137 43 78.8%
>5% EBWG 169 45 79.9%
Ali [10]
Retrospective
WL > 10% TBW 23 42.7 73.9%
Supportive
WL 5–10% TBW 102 43 87.3%
WL 0–5% TBW 135 42.8 95.5%
WG % TBW 91 42.1 96.7%
Fujioka [11]
Retrospective
WL (>0 lbs) 55 49 80.0%
Supportive
WG (<0 lbs) 66 48 86.4%
Harnisch [12]
Retrospective
WL (
≥10 lbs) 88 44 84.1%
Supportive
WG (
≥10 lbs) 115 41.4 85.2%
Huerta [13]
Retrospective
WL 15 50 33.3%
Inconclusive
WG (non-WL) 25 50 28.0%
WL: weight loss; WG: weight gain; EBW: excess body weight; TBW: total body weight.
P1
P2
y
=
1x +0.38
P3
P4
P5
P6
Percentage weight Loss (based on IW at surgery)
Percent IW loss before surgery (based on IW at surgery)
5 101520
55
60
50
45
40
35
Figure 4: Example of regression. Study includes six hypothetical
patientswholostweightpreoperatively.Thepreoperativeweight
loss is graphed against their complete program weight loss (from
initial consultation to one year after operation).
TheBclassstudybyHuertaetal.[13] was considered
inconclusive as the followup was less than 50% during the
first year and only had postoperative data for the second and
fourth years after surgery.
3.3. Regression Studies. The study by Alger-Mayer et al.
[16], which was done at Albany, NY, was analyzed using
regression. Even though the year 3 and 4 results supported
our hypothesis, the results were considered inconclusive
because the paper lacked postoperative data in the first year
after gastric bypass.
ThestudybyJantzetal.[14] was inconclusive because
they were not looking at immediate preoperative weight loss.
Carlin et al. [17] published a paper that changed weight
loss requirements based on the initial BMI. Those individuals
that had BMI greater than 60 had to lose more than those
that were less than 50 kg/m
2
. Thus, the study was considered
inconclusive due to difficulty interpreting the methodology.
The study by Alvarado et al. [15] identified a 1.8%
increase in the % EWL one year after gastric bypass w ith each
1% total body weight lost preoperatively. This retrospective
study was considered supportive due to the positive effect
preoperative weight loss would have on postoperative weight
loss in the absence of controlling for initial weig h t at surgery.
Results are summarized in Ta bl e 3.
3.4. Rejected Studies. The study by Riess et al. [18]was
rejected as a study because the weight loss group and the
weight gain group had statistically significant difference in
mean weight at both initial consultation and the time before
surgery. The difference was preserved postoperatively (see
Table 4).
4. Discussion
Our study found that weight at the time of surgery, rather
than the amount of weight lost preoperatively, determines
the weight loss outcome postoperatively. Stated differently,
weight at a given time period after surgery is the same
percent of initial body weight independent of starting weight.
For example, if a patient weighs 160 kg at the time of
surgery, he will weigh approximately 62% of that at one
year after surgery or 100 kg. If he lost 22.5 kg preoperatively
Journal of Obesity 5
Class-A study
Rejected
No
Class B study
No
No No
Regression study
Selected study
Are the groups of patients similar mean
weight at the time before operation?
Are the groups of patients similar
mean weight at initial consultation?
Are the groups of patients similar mean
weight at the time before operation?
Are the patients divided into
WL and WG groups?
Yes
Yes Yes
Yes
Figure 5: Flow chart depicting the classification of the selected studies into Class A, B, and regression studies. WL: weight loss; WG: weight
gain.
Table 3: Regression studies.
Lead author Study design Patients Mean age Operation type Female (%) Results
Jantz [14] Retrospective 384 43.3 LRYGB 82.5 Inconclusive
Alvarado [15] Retrospective 90 42 LRYGB 90 Supportive
Sharon Alger
[16]
Prospective 150 45.3 RYGB
∗
80 Inconclusive
Carlin [17] Retrospective 295 45 LRYGB 88.8 Inconclusive
LRYGB: laparoscopic roux-en-y gastric bypass;
∗
RYGB: Roux en Y Gastric Bypass. the roux-en-y gastric bypass was an open procedure.
and weighed 136 kg at the time of surgery, he would weigh
62% of his initial body weight or 81.5 kg . His overall
weight loss would be 13.5 kg greater for having lost 22.5 kg
preoperatively. Since weight loss following gastric bypass
tends to be negligible after one year, this probably represents
a real gain. In this paper, we have detailed two classes of
studies, A and B. Combining review data with previous
work by Sczepaniak et al. [6], it is possible to create visual
representation of both studies. Class A and class B studies are
shown in Figures 2 and 3, respectively. Both groups changed
in mean weight at initial consultation, one group gaining
weight and the other losing weight. Preoperative weight gain
and loss were arbitrarily set for explanation purposes. In a B
class study it is observed that the means of both the weight
loss and weight gain groups is not different for the first year.
With regards to regression study, in the six hypothetical
patients, the relationship to preoperative weight loss can now
be clearly seen from Figure 6. The more preoperative percent
initial body weight loss (based on initial weight at surgery),
the more the percent total body weight loss (calculated from
6 Journal of Obesity
36812
Percent initial weight at surgery
120
110
100
90
80
70
60
62%
P2
P4
P3
P5
P6
P1
Time after operation (months)
Consultation Surgery
Figure 6: Hypothetical regression model. This model demonstrates
the effect of preoperative weight loss in gastric bypass patients.
Table 4: Rejected Studies
Lead
author
Study design Group Patients Age
Female
(%)
Riess et
al. [18]
Retrospective
WL 74 43.4 70.3%
WG
(non-WL)
279 42.7 86.4%
WL: weight loss; WG: weight gain.
subtract ing percent total body weight at initial consultation
from achieved percent total body weight after surgery), see
Figure 6.
From the graph on the hypothetical patients in Figure 4,
it is now possible to see the benefit of losing preoperative
weight on an individual level.
Our study has only dealt with studies having gastric
bypass surgeries, but the preoperative weight loss might have
a similar role in sleeve gastrectomy and sleeve plication (also
current methods for weight reduction).
Losing weight leads to b etter outcomes because a patient
entering surgery with a lower weight than someone entering
surgery without weight loss will have more weig ht loss in
total.
5. Conclusion
Our review of the literature supports the idea that weight
loss after surgery for gastric bypass, and by extension other
procedures as well, is a percent of initial body weight.
Moreover, the literature is generally supportive of the idea
that short-term preoperative weight loss is additive, that is,
increases the total amount of weight lost.
Conflict of Interests
The authors have no commercial associations that might be
a conflict of interest in relation to this paper.
Acknowledgments
TheauthorsaregratefultoSanDiegoUniversity,CA;St.
George’s University Grenada, WI; Amit Kulkarni, MBBS—
Mayo Clinic, Rochester; Adel Youssef MD, Gastroenterology
Clinic,Warren, OH. They would also like to thank the many
others who made this work possible.
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