Objective: Data on taste acuity after bariatric surgery are scarce, and taste perception after sleeve gastrectomy, to our knowledge, has never been investigated. The objective of this work was to retrospectively compare taste acuity and sweetness acceptability after Roux-en-Y gastric bypass and sleeve gastrectomy. Methods: Subjects with a postoperative period
6 mo were recruited (between January and June 2012) for a non-randomized, observational study. Subjects completed sensory evaluation sessions consisting of measurement of detection thresholds for bitterness and sweetness (N = 21), saltiness and sourness (N = 19), and sweetness acceptability (N = 19). Significance was established with Tukey’s honest significant difference test and analysis of variance using the SAS GLM procedure. Results: Sourness threshold was significantly higher among subjects who had undergone Roux-enY gastric bypass (P = 0.0045). No other differences were obtained for the other thresholds or sweetness acceptability (P > 0.05). Conclusions: Further randomized studies are needed to clarify these differences.

1. Brief report
Effect of Roux-en-Y gastric bypass and sleeve gastrectomy on
taste acuity and sweetness acceptability in postsurgical subjects
Sibelle El Labban M.S. a
, Bassem Safadi M.D. b
, Ammar Olabi Ph.D. a,*
a
Nutrition and Food Sciences Department, Faculty of Agricultural and Food Sciences, American University of Beirut, Beirut, Lebanon
b
Surgery Department, Internal Medicine, Faculty of Medicine, American University of Beirut, Beirut, Lebanon
a r t i c l e i n f o
Article history:
Received 21 November 2015
Accepted 23 March 2016
Keywords:
Gastric bypass
Sleeve gastrectomy
Food preferences
Taste
a b s t r a c t
Objective: Data on taste acuity after bariatric surgery are scarce, and taste perception after sleeve
gastrectomy, to our knowledge, has never been investigated. The objective of this work was to
retrospectively compare taste acuity and sweetness acceptability after Roux-en-Y gastric bypass
and sleeve gastrectomy.
Methods: Subjects with a postoperative period !6 mo were recruited (between January and June
2012) for a non-randomized, observational study. Subjects completed sensory evaluation sessions
consisting of measurement of detection thresholds for bitterness and sweetness (N ¼ 21), saltiness
and sourness (N ¼ 19), and sweetness acceptability (N ¼ 19). Significance was established with
Tukey’s honest significant difference test and analysis of variance using the SAS GLM procedure.
Results: Sourness threshold was significantly higher among subjects who had undergone Roux-en-
Y gastric bypass (P ¼ 0.0045). No other differences were obtained for the other thresholds or
sweetness acceptability (P > 0.05).
Conclusions: Further randomized studies are needed to clarify these differences.
Ó 2016 Elsevier Inc. All rights reserved.
Introduction
The prevalence of adult obesity (body mass index [BMI]
!30 kg/m2
) has reached worrisome levels in the Middle East,
particularly in Lebanon, where it significantly increased from
17.4% to 28.2% within a period of 12 y (1997–2009) [1].
Bariatric surgery appears to be an effective and lasting pro-
cedure for extreme obesity when other measures do not yield
the target weight loss. Although Roux-en-Y gastric bypass (RYGB)
is the most commonly performed bariatric surgery worldwide,
global trends have indicated a considerable increase in the
number of sleeve gastrectomies (SGs) performed from 2003 to
2011 [2].
The effects of obesity surgery on taste detection have been
assessed by investigators in an attempt to physiologically explain
the changes in food preference, and are controversial across the
literature. Previous taste acuity studies with RYGB have yielded
mixed results, with significant differences between pre- and
postsurgery for bitter and sour tastes only [3], a significant
decline only in sweet recognition threshold [4], and a higher
sensitivity for sweet taste [5].
To date, no study has assessed taste acuity differences be-
tween prospective RYGB and SG subjects. An understanding of
the changes in taste acuity and sweetness acceptability, and food
preferences in general, is essential for maintaining long-term
weight loss postsurgery and for developing improved follow-
up strategies. The objective of this pilot study was to compare
the effects of RYGB and SG on taste acuity and sweetness
acceptability in postsurgical subjects.
Material and methods
Study design and subject recruitment/selection
A total of 21 subjects who had undergone either RYGB or SG were recruited
throughout a 6-mo period (January–June 2012) in a retrospective fashion from
the bariatric surgery database available at the American University of Beirut
(AUB) Medical Center, a private hospital, to participate in this study. Subjects
fulfilled the inclusion and exclusion criteria, which were as follows: 1) post-
operative period !6 mo; 2) no pregnancy, 3) no substance abuse (alcohol or
drugs); 4) no severe medical/psychological illness that would prevented
participation, 5) no history of major operations on the gastrointestinal tract,
and 6) no major postoperative complications after bariatric surgery. Evaluation
of taste acuity and sweetness acceptability took place at the AUB sensory
* Corresponding author. Tel: (961)1-374374, ext. 4500; fax: (961)1-744460.
E-mail address: Ammar.olabi@aub.edu.lb (A. Olabi).
http://dx.doi.org/10.1016/j.nut.2016.03.022
0899-9007/Ó 2016 Elsevier Inc. All rights reserved.
Contents lists available at ScienceDirect
Nutrition
journal homepage: www.nutritionjrnl.com
Please cite this article in press as: El Labban S, et al., Effect of Roux-en-Y gastric bypass and sleeve gastrectomy on taste acuity and
sweetness..., Nutrition (2016), http://dx.doi.org/10.1016/j.nut.2016.03.022
Nutrition xxx (2016) 1–4

2. laboratory. The institutional review board at AUB approved the study protocol,
and all participants were provided with and submitted an individually written
informed consent.
Data collection
Demographic and anthropometric measurements
Demographic data and characteristics of the subjects (sex, age, height, weight
before and after surgery, preoperative comorbidities, and date of bariatric sur-
gery) were obtained from the patients’ medical records. These were independent
of the taste tests in terms of timeline and were recorded 1 y postoperatively
because most of the weight loss would have occurred by then and the weight
tends to stabilize afterward.
Sensory evaluation of taste acuity
Two types of sensory tests were conducted: the 3-Alternative Forced Choice
(3-AFC) test to measure recognition thresholds for the four basic tastes (salt, sour,
sweet, and bitter), and a sweetness acceptability test to measure acceptability for
different sucrose solutions.
The 3-AFC test was administered using the ascending method of limits [6],
whereby nine stimulus levels for each taste were selected based on preliminary
tests and previous studies and standards found in the literature [7,8]. The 3-AFC
at each level had one sample as the stimulus and two other blank solutions [7,
8]. Participants were asked to identify the sample that was more intense on a
specific taste. Stimulus solutions for sweetness, sourness, saltiness, and
bitterness consisted of dissolving 10.95 g sucrose, 0.54 g citric acid 1-hydrate,
3.65 g sodium chloride, and 0.078 g quinine sulfate in 500 mL water, respec-
tively, resulting in corresponding initial concentrations of 64 mmol/L,
8 mmol/L, 112 mmol/L, and 200 mmol/L, respectively, for the tastes (highest
levels, level 9). Subsequently, eight less concentrated stimulus levels for each
taste were prepared using a dilution factor of 2 of the previous level. One
ascending series was used for each basic taste, starting with the lowest level
and following a geometric progression of a factor of 2 up to the highest (ninth
level) indicated in the aforementioned concentrations. Twenty-one subjects (12
from the SG group and 9 from the RYGB group; 70% response rate) completed
the bitterness and sweetness threshold tests and 19 of the 21 (11 from the SG
group and 8 from the RYGB group) completed the saltiness and sourness
threshold tests, with 2 subjects dropping out and not completing the latter
threshold tests. In the sweetness acceptability test, subjects (N ¼ 19, 11 from the
SG group and 8 from the RYGB group) were provided with ascending concen-
trations of sucrose (2%, 4%, 6%, 8%, 10%, 12%, 20%, 30%, and 40%) and asked to rate
their acceptability on the 9-point hedonic scale [8]. Sugar-free Kool Aid sachets
were used for the acceptability test, and the sugar concentrations were adjusted
using a hand-held Brix refractometer (RHB 0-80).
The threshold and acceptability tests were conducted in two sessions: Each
session included a 3-AFC test for two basic tastes, and one of either session
covered the acceptability test for sucrose solutions. All samples were prepared in
batches 1 d before the evaluation sessions and stored at 4C until serving.
Samples were served, at room temperature, in 50-mL plastic cups coded with
three-digit random numbers. The serving sequence of samples was counter-
balanced among the panelists for each level, as was the sequence of the different
basic tastes set [9]. Subjects were seated in individual booths with white fluo-
rescent lighting and were provided with a tray containing the samples, a cup of
water for palate rinsing between ascending levels (subjects were expectorating
the water to avoid digestive discomfort that could be caused by the small volume
of the stomach postsurgery, which could be filled up quickly with any amount of
fluid), napkins, and the sensory questionnaire to write their answers. Subjects
were allowed to rest for 5 to 10 min, depending on preference, between tests.
Subjects attended the evaluation sessions at different times of the day (mostly
between 09:00 h and 16:00 h), depending on their availability. They were
instructed not to eat or drink anything (except water if need be) 2 h before the
start of either session so that their taste palatability would not be affected. Both
evaluation sessions averaged 30 to 40 min in total.
Data and statistical analysis
The main variables were three continuous variablesdage (y), weight (kg),
and postoperative period (mo)dand three discrete variablesdsex (male-female),
surgery type (RYGB-SG), and preoperative comorbidities classified into three
groups (none, one comorbidity, and two or more comorbidities). The post-
operative period was time elapsed from surgery date to the date of the initial
interview with the dietitian. All statistical analyses were performed in SAS sta-
tistical software (Version 9.02, SAS Institute, Cary, NC). Significant means were
separated by Tukey’s honest significant difference test. Analysis of variance was
performed using the GLM procedure. Recognition thresholds for taste acuity
were calculated as the geometric mean of concentrations between an incorrect
response and a correct response that is followed only by correct responses.
Results
Participants ranged between 20 and 62 y in age. Despite the
seemingly large difference in age between the subjects of the
two groups (RYGB and SG), there was no significant age differ-
ence, and the two groups did not differ on any of the variables
(Table 1).
There were no significant differences between RYGB and SG
subjects for the taste thresholds of sweetness, saltiness, and
bitterness. However, RYGB and SG subjects significantly differed
in sourness thresholds. The threshold was higher, and hence the
sensitivity lower, among RYGB subjects than among SG subjects
(2.51 Æ 2.5 versus 1.16 Æ 0.9, P ¼ 0.0045) (Fig. 1). There was no
significant difference in sweetness acceptability despite a
slightly higher mean rating, across all sucrose concentrations,
among SG subjects compared with RYGB subjects (4.9 Æ 2.8
versus 4.8 Æ 2.3, P 0.05) (Fig. 2). Sweetness level, i.e., the
different sucrose concentrations, was also naturally significantly
different (P 0.001) for sweetness acceptability. When the mean
ratings for acceptability of RYGB and SG subjects for each sucrose
concentration (2%, 4%, etc.) were compared, there were no sig-
nificant differences between the two subject groups for all con-
centration levels, despite the trend of higher ratings for SG
subjects for all concentrations, notably for last three sucrose
concentrations (20%, 30%, and 40%) (Fig. 2).
Discussion
Our findings revealed a significantly higher sourness
threshold, with no significant differences in either the other taste
thresholds or acceptability, among RYGB subjects compared with
SG subjects. Scruggs et al. obtained a significant increase in
sensitivity for sourness at 60 d postoperatively for RYGB
compared to baseline values [3]. Both Scruggs et al. [3] and Burge
et al. [4] obtained lower thresholds, i.e., higher sensitivity, for
sweetness recognition after RYGB. Alterations in food prefer-
ences and eating behavior may be secondary to changes in taste
acuity after bariatric surgery [4,5]. One mechanism suggested for
RYGB is its modulation of the sensory signal by altering its in-
tensity or quality, hence leading to a change in palatability [10].
Table 1
Demographic and anthropometric measurements of subjects
Variable Roux-en-Y
gastric bypass
(n ¼ 9)
Sleeve
gastrectomy
(n ¼ 12)
P value
Sex 0.056*
Males 6 (67) 3 (25)
Females 3 (33) 9 (75)
Age (y) 37.0 Æ 11.0 28.4 Æ 7.2 0.065
Comorbiditiesy
0.586*
0 5 (56) 9 (75)
1 2 (22) 2 (17)
!2 2 (22) 1 (8)
Postoperative period (mo) 16.8 Æ 14.5 22.8 Æ 11.7 0.329
Weight (kg)
Preoperative 125.6 Æ 17.6 115.1 Æ 26.9 0.297
Postoperativez
87.4 Æ 21.4 79.2 Æ 17.6 0.366
Body mass index (kg/m2
)
Preoperative 42.8 Æ 3.6 41.3 Æ 4.7 0.400
Postoperativez
29.7 Æ 5.7 28.6 Æ 3.9 0.634
Data are expressed as the mean Æ SD or n (%)
* P value calculated using the c2
test.
y
Preoperative comorbidities: 0 ¼ none or absence of comorbidities;
1 ¼ presence of one comorbidity; !2 ¼ presence of two or more comorbidities.
z
Mean values 1 y after surgery.
S. El Labban et al. / Nutrition xxx (2016) 1–42
Please cite this article in press as: El Labban S, et al., Effect of Roux-en-Y gastric bypass and sleeve gastrectomy on taste acuity and
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3. Another hypothesis is hedonic stimulation of the brain, in
mediation with specific gut hormones, and the creation of
visceral malaise after ingestion of fat or sugar, whereby in-
dividuals learn to avoid high-calorie foods because of the un-
desirable adverse reactions these foods may cause [10]. On the
other hand, Bueter et al. reported that RYGB patients had the
same hedonic taste ratings of sucrose preoperatively and post-
operatively, which means their rating was not affected by
changes in sucrose taste detection postoperatively, namely lower
detection threshold and increased sensitivity [11]. However, the
persisting trend of higher perception and increased sensitivity
for the sweet taste after RYGB surgery remains partly responsible
for the aversion of high-calorie foods and the adaptation of
healthier food choices by this surgery group postoperatively [5].
Another point to consider is the noticeable difference in the
proportions of female subjects in the two surgical groups (33% in
RYGB versus 75% in SG), which could have influenced the results,
as menstrual cyclical changes have been found to affect taste
preferences, particularly sweetness, in females [12,13]. Saluja
et al. reported that postmenopausal women had a reduced
perception or sensitivity for the sweet taste, which was depicted
in a change in their eating habits with an expressed liking for
sweeter food [12]. Elliott et al. found that mean taste preference
ratings for sucrose fluctuated throughout the menstrual cycle;
they were lowest during the luteal phase, and were higher in the
early follicular phase or menstrual phase [13]. No definite com-
parison can be made with our results given that there were only
three females in the RYGB group and measurements with respect
to menopausal or menstrual stages are lacking. Obviously, eating
behavior and food preferences are influenced by several factors
including the effect of smell on food acceptability and flavor
detection. Holinski et al. reported a significant effect of bariatric
surgery (RYGB, SG and gastric banding) on gustatory and olfac-
tory functions; however, this effect dissipated after 6 mo of
surgery [14]. Other recent studies have attempted to assess
prospective measurements of reported taste and olfactory
changes after RYGB and SG and found no major differences in
taste and smell changes for the two procedures, although
this study relied on a survey rather than on taste and olfactory
tests [15].
Our study has some limitations. A larger number of subjects
and specific postoperative periods, or repeated measures over
time, would have allowed more comprehensive conclusions.
Future research should preferably include the comparison of
preoperative and postoperative measurements and olfactory
measurements, as well as a non-surgical control group, to allow
for better interpretation as to whether the two types of surgery
have similar effects on thresholds and acceptability ratings of
sucrose solutions compared with controls or do not have an ef-
fect on taste acuity.
Fig. 1. Mean thresholds and standard errors of the means for sweetness (mmol/L),
sourness (mmol/L), saltiness (mmol/L), and bitterness (mmol/L) for Roux-en-Y
gastric bypass (gray) and sleeve gastrectomy (black). *P 0.05.
Fig. 2. Least-squares acceptability means and standard errors of the means for the sweet solutions (2%, 4%, 6%, 8%, 10%, 12%, 20%, 30%, and 40% sucrose) for Roux-en-Y gastric
bypass (gray) and sleeve gastrectomy (black).
S. El Labban et al. / Nutrition xxx (2016) 1–4 3
Please cite this article in press as: El Labban S, et al., Effect of Roux-en-Y gastric bypass and sleeve gastrectomy on taste acuity and
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4. Conclusions
Only the sourness threshold was found to be significantly
higher among RYGB subjects as compared with SG subjects, an
interesting finding that warrants further investigation. RYGB
subjects also had lower sensitivity, although not significantly, to
sweet and bitter tastes and higher sensitivity to the salt taste
compared with their SG counterparts. As for sweetness accept-
ability, SG subjects had higher mean ratings for all sucrose con-
centrations compared with RYGB subjects. To our knowledge,
this work is the first pilot study to examine differences in taste
acuity and sweetness acceptability between RYGB and SG sub-
jects. If prospective studies were to follow, special attention
should be given to the inclusion of a control group. Further
research that integrates sensory tests with biochemical mea-
surements, such as appetite hormones, and behavioral mea-
surements, such as food choices and clinical symptoms, has the
potential to provide a comprehensive picture of the different
mechanisms involved and the magnitude of their interactions, if
present, thus possibly providing clearer insight into successful
weight loss strategies.
Acknowledgments
This study was funded by the University Research Board at
the American University of Beirut.
The authors thank Dr. Sami Masri for recruiting patients;
Loulwa Kalache for her assistance in the statistical work; Hamza
Daroub, Farida Otaki, Sahar Abou Lteif, Riwa Chidiac, Nazha Abou
Ghali, and Hanin Saleh for their assistance in conducting the
taste acuity sessions; and Roy Nassif for his help with the figures.
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