Efficacy and Mechanisms of Gastric Volume-Restriction Bariatric Devices

Abstract

Obesity is a chronic disease that affects over 795 million people worldwide. Bariatric surgery is an effective therapy to combat the epidemic of clinically severe obesity, but it is only performed in a very small proportion of patients because of the limited surgical indications, the irreversibility of the procedure, and the potential postoperative complications. As an alternative to bariatric surgery, numerous medical devices have been developed for the treatment of morbid obesity and obesity-related disorders. Most devices target restriction of the stomach, but the mechanism of action is likely more than just mechanical restriction. The objective of this review is to integrate the underlying mechanisms of gastric restrictive bariatric devices in obesity and comorbidities. We call attention to the need for future studies on potential mechanisms to shed light on how current gastric volume-restriction bariatric devices function and how future devices and treatments can be further improved to combat the epidemic of obesity.

Full text

fphys-12-761481 October 22, 2021 Time: 14:39 # 1
MINI REVIEW
published: 28 October 2021
doi: 10.3389/fphys.2021.761481
Edited by:
Kathleen S. Curtis,
Oklahoma State University Center
for Health Sciences, United States
Reviewed by:
Carmen De Miguel,
University of Alabama at Birmingham,
United States
Zhi Yi Ong,
University of New South Wales,
Australia
*Correspondence:
Ghassan S. Kassab
gkassab@calmi2.org
Specialty section:
This article was submitted to
Metabolic Physiology,
a section of the journal
Frontiers in Physiology
Received: 19 August 2021
Accepted: 07 October 2021
Published: 28 October 2021
Citation:
Wang Y and Kassab GS (2021)
Efficacy and Mechanisms of Gastric
Volume-Restriction Bariatric Devices.
Front. Physiol. 12:761481.
doi: 10.3389/fphys.2021.761481
Efficacy and Mechanisms of Gastric
Volume-Restriction Bariatric Devices
Yanmin Wang and Ghassan S. Kassab*
California Medical Innovations Institute, San Diego, CA, United States
Obesity is a chronic disease that affects over 795 million people worldwide. Bariatric
surgery is an effective therapy to combat the epidemic of clinically severe obesity,
but it is only performed in a very small proportion of patients because of the limited
surgical indications, the irreversibility of the procedure, and the potential postoperative
complications. As an alternative to bariatric surgery, numerous medical devices have
been developed for the treatment of morbid obesity and obesity-related disorders. Most
devices target restriction of the stomach, but the mechanism of action is likely more
than just mechanical restriction. The objective of this review is to integrate the underlying
mechanisms of gastric restrictive bariatric devices in obesity and comorbidities. We call
attention to the need for future studies on potential mechanisms to shed light on how
current gastric volume-restriction bariatric devices function and how future devices and
treatments can be further improved to combat the epidemic of obesity.
Keywords: obesity, weight loss, medical device, restrictive procedure, review
INTRODUCTION
Obesity is a consequence of caloric imbalance and excessive fat accumulation. The World Health
Organization (WHO) defined obesity as body mass index (BMI) over 30, while 25–30 is considered
overweight. Obesity is a major public health problem in the developed world, which significantly
increases the risk of multiple diseases and disorders such as type 2 diabetes mellitus, hypertension,
heart disease, and cancer. The prevalence of obesity has greatly increased in the past decades. It was
estimated that in 2016, the number of children/adolescents and adults that suffered from obesity
worldwide were 124 and 671 million, respectively (Bentham et al., 2017). In addition, 213 million
children/adolescents and 1.3 billion adults were in the range of overweight (Bentham et al., 2017).
In the US, the prevalence of obesity in adults and children ages 6–11 old has reached over 35%
(Flegal et al., 2012) and 17% (Ogden et al., 2016).
In various countries and regions, bariatric surgery has been listed in obesity management
guidelines as the most effective way to treat morbid obesity and the related disorders (Jensen et al.,
2014;Yumuk et al., 2015;Wharton et al., 2020). The most popular procedures (American Society
for Metabolic and Bariatric Surgery, 2021) gastric bypass and sleeve gastrectomy are, however, not
readily accepted by many patients because both include removal of some part of the stomach, and
this gastrectomy may induce severe complications. Only 1–2% of the eligible candidates undergo
bariatric surgery for obesity each year in the US (Gasoyan et al., 2019). Furthermore, based on
Western guidelines, patients whose BMI is lower than 35 (or 40 without adiposity-related disease)
are beyond the indications of bariatric surgery and thus lack effective treatments.
As less invasive alternatives, many gastric restrictive bariatric devices such as gastric band,
intragastric balloons, and so on, have been used for combating obesity and some achieve
Frontiers in Physiology | www.frontiersin.org 1October 2021 | Volume 12 | Article 761481

fphys-12-761481 October 22, 2021 Time: 14:39 # 2
Wang and Kassab Mechanisms Underlying Restrictive Devices
comparable efficacy to surgeries (Vargas et al., 2018). Although
most of the devices are intended to restrict the stomach to
decrease calorie intake, the mechanisms of action for the
considerable weight loss following gastric volume-restricted
bariatric devices are not fully appreciated. This review aims to
integrate the potential mechanisms through which restrictive
bariatric devices induce weight loss and metabolic improvements.
To the best of our knowledge, this is the first review on this topic.
Gastric Band
In the adjustable gastric banding (AGB) procedure, an adjustable
silicone band is placed around the stomach below the gastro
esophageal junction to restrict the dilation of the gastric pouch
as shown in Figure 1A. AGB is the most well-known gastric
restrictive device: first implanted in 1983 (Kuzmak, 1991), it
gained popularity in early twenty-first century (Favretti et al.,
2009;Ibrahim et al., 2017). A meta-analysis (Garb et al., 2009)
found that the excess weight loss (weight loss/pre-operative
excess body weight ×100%) post-AGB was 42.6% at 1 year,
50.3% at 2 years, and 55.2% at over 3 years. Another meta-
analysis (Golzarand et al., 2017) showed that AGB induced nearly
48% excess weight loss at either 5 or 10 years postoperatively.
According to data from 20 years follow-up in patients with
obesity, AGB was associated with significantly lower incidence
of diabetes, cardiovascular diseases, cancer, and renal diseases
(Pontiroli et al., 2018). The cost for AGB is significantly lower
than that for Roux-en-Y gastric bypass or sleeve gastrectomy
(SG) (Doble et al., 2019). Some studies, however, reported
that AGB failed to maintain reduced body weight or control
obesity-related morbidities (Pournaras et al., 2010;Chang
et al., 2014;Park et al., 2019). Worse still, additional studies
showed that patients who underwent AGB may need a second
surgery due to band migration or erosion, pouch dilatation,
achalasia or megaesophagus, stomach obstruction, or other
severe complications (Arias et al., 2009;Chang et al., 2014;
Kodner and Hartman, 2014;Tsai et al., 2019). The reported
reoperation rate was up to 82.7% in 15-year follow-up (Tsai et al.,
2019). As a result, the popularity of AGB has been dramatically
decreased in the past decade. In recent years, several improved
AGB devices and systems (Billy et al., 2014;Edelman et al.,
2014;Ponce et al., 2014) have been developed, but the long-term
effects remain unclear. In 2019, AGB only accounted for 0.9% of
bariatric procedures in the US (American Society for Metabolic
and Bariatric Surgery, 2021).
There have been numerous studies focused on the potential
mechanism of AGB in weight control and metabolic amelioration
induced by the placement of the band. AGB is considered to
improve eating behavior such as alleviating binge eating disorders
and decreasing emotional eating and night eating in the short
term (Opozda et al., 2016;Hindle et al., 2020), whereas long-
term results are inconsistent (Opozda et al., 2016;Smith et al.,
2019). Monteiro et al. (2007) compared AGB rats and pair-fed
rats, observing that AGB rats were leaner. This study suggests
that additional factors beyond restriction exist. It seems that
gastric motility, neural activity, ghrelin level, concentrations
of gut hormones, energy expenditure, bile acids metabolism,
and gut microbial diversity play important roles; however, the
conclusions varied significantly (Wang et al., 2019). For example,
Aron-Wisnewsky et al. (2019) observed that gut microbial gene
abundance increased after AGB whereas Lee et al. (2019) reported
an opposite result. Another example is that ghrelin levels were
found to be unchanged (Sysko et al., 2013), increased (Kawasaki
et al., 2015), or decreased (Leonetti et al., 2003) following
AGB. We assume that the variations are not only partly due
to the differences in techniques of the procedures and baseline
conditions of the subjects, but also because the underlying factors
are complex (i.e., multiple mediators work together and interact
with each other).
In addition to AGB in which the stomach is restricted
horizontally, vertical banded gastroplasty (VBG) used banding
above the crow’s foot of Latarjet’s nerve along with vertical
staple line toward the angle of His to restrict the stomach.
In the early 1980s, Mason (1982) reported that VBG caused
more weight loss and less complications when compared with
other surgical procedures. Kellum et al. (1990) reported that
at 6 months after VBG, excess weight loss in patients with
morbid obesity was 41.8%. Brolin et al. (1994) found that patients
underwent VBG preferred to eat high-caloric food, resulting
in postoperative weight regain. Olbers et al. (2006) obtained
similar results, showing that VBG patients consumed more
sweet foods and less vegetables and fruits. One study (Amsalem
et al., 2014) revealed that VGB (specifically the silastic ring
vertical gastroplasty) as well as AGB significantly lower the
risk of pregnancy complications such as gestational diabetes
mellitus and hypertension. This suggests that some metabolic
factors exist in these restrictive procedures, which requires
further research. In Kellum et al. (1990)’s study, glucose, insulin,
enteroglucagon, serotonin, vasoactive intestinal polypeptide, and
cholecystokinin (CCK) responses to meals were not changed after
VBG. Tremaroli et al. (2015) suggested that VBG has long-term
positive effects on gut microbiota and bile acids. The resting
energy expenditure was reported to be decreased after VBG,
but it seemed a reflection of weight loss instead of the reason
(Olbers et al., 2006). Similar to AGB, however, long-term studies
(Balsiger et al., 2000;van Wezenbeek et al., 2015;Froylich et al.,
2020) revealed that the weight reduction after VBG was not
sustained and complications such as pouch dilatation, staple-line
disruptions, and outlet stenosis were frequent. Therefore, VBG
lost popularity and is no longer practiced.
Gastric Sleeve Implant and Gastric Clip
Since so-called restrictive procedures are technically simple, there
have been several devices designed to treat obesity by reducing
gastric volume, apart from traditional gastric banding devices,
in either laboratory or clinical settings. Our group developed
a restrictive device (referred to as Gastric Sleeve Implant,
GSI), which is designed to be laparoscopically implantable and
removable (Guo et al., 2011, 2014) as shown in Figure 1B. When
placed loosely on the outside (serosa) of the stomach, the device
generates a sleeve-shaped pouch similar to sleeve gastrectomy
(SG) but avoids the irreversibility of the SG because it does not
require stapling or gastrectomy. When the stomach is empty,
GSI does not compress the stomach, which reduces the risk of
device migration or tissue necrosis. GSI also has two C-rings to
Frontiers in Physiology | www.frontiersin.org 2October 2021 | Volume 12 | Article 761481

fphys-12-761481 October 22, 2021 Time: 14:39 # 3
Wang and Kassab Mechanisms Underlying Restrictive Devices
FIGURE 1 | Schematic of gastric restrictive bariatric devices. (A) Adjustable gastric banding (AGB). Used with permission of the Radiological Society of North
America (RSNA R
) (Sonavane et al., 2012). The band is planted around the stomach below gastroesophageal (GE) junction. (B) Gastric sleeve implant (GSI).
Reprinted by permission from Springer Nature, Obesity Surgery, Efficacy of a Laparoscopic Gastric Restrictive Device in an Obese Canine Model, Guo et al. (2014)
COPYRIGHT 2013. The device is mounted on the lesser curvature and creates a vertical sleeve food track. (C) Intragastric balloons (IGB). Used with permission of
Mayo Foundation for Medical Education and Research, all rights reserved
(https://www.mayoclinic.org/medical-professionals/endocrinology/news/intragastric-balloon- a-re-emerging-approach-for-obesity/mac-20430245). The inflated
balloon occupies some intragastric space.
prevent the distension of the sleeve (Guo et al., 2011, 2014). The
GSI is safe, effective and has been proven removable in animals
(Guo et al., 2011, 2014). In a canine model, the excess weight
loss reached 75% at 12 weeks after procedure but returned to
22% at 6 months after the removal of the device (Guo et al.,
2014). To explore the underlying mechanism, our canine and
rat studies (Guo et al., 2012) showed an elevated level of ghrelin
and a reduced concentration of leptin after the implantation of
GSI, which returned to normal levels after GSI removal. We
assume that GSI induces an adaptive or compensatory increase in
ghrelin secretion at early stages after surgery due to the integrity
of stomach, which would counteract additional weight loss and
cause the corresponding body weight recovery after its removal
(Guo et al., 2012). The lower leptin level induced by GSI is highly
correlated with weight loss. It is probably secondary to weight
loss as serum leptin concentration reflects the total amount of fat
mass in the body (Guo et al., 2012). The Glucagon-like peptide-1
(GLP-1) concentration was found to be unchanged.
Subsequently, a device with similar principle, the vertical
gastric clip (Jacobs et al., 2017;Noel et al., 2018) or BariClip
(Noel et al., 2020), was used in patients. Parallel to the lesser
curvature, the device separates a medial lumen from an excluded
lateral gastric pouch (Jacobs et al., 2017). The reduction of BMI
and % excess weight loss were 12.7 and 66.7, respectively, at
2 years after the operation (Jacobs et al., 2017). In addition, the
quality of life was improved in more than 90% of patients (Noel
et al., 2018). A simpler device named Gastric Clip (Chao et al.,
2019) was also used in clinics. The gastric clip creates a transverse
gastric partition when obliquely applied to the upper fundus
(Chao et al., 2019). One year after surgery, BMI was significantly
reduced from 44 to 37 kg/m2, and the total weight loss (weight
loss/pre-operative body weight ×100%) was 23.5%. Diabetes and
hyperlipidemia were effectively alleviated as well (Chao et al.,
2019), and the effects were much better when combined with
a proximal jejunal bypass. The possible mechanisms underlying
clip-induced weight change require further studies. The long-
term benefits of these devices are currently lacking, however, and
some patients were reported to suffer from gastric obstruction or
insufficient weight loss after such procedures and thus underwent
clip removal or revisional surgery (de la Plaza Llamas et al., 2020;
Frontiers in Physiology | www.frontiersin.org 3October 2021 | Volume 12 | Article 761481

fphys-12-761481 October 22, 2021 Time: 14:39 # 4
Wang and Kassab Mechanisms Underlying Restrictive Devices
TABLE 1 | Parameter changes after gastric volume-restriction bariatric devices.
Adjustable gastric
banding (AGB)
Vertical banded
gastroplasty
(VBG)
Gastric sleeve
implant (GSI)
Intragastric balloons
(IGB)
Endoscopic
sleeve
gastroplasty
(ESG)
Articulating
circular
endoscopic
(ACE)
Gastric emptying ↔ ↓ ↓ ↓
Energy expenditure ↑ ↔ ↓ ↓ ↓
Ghrelin level ↑ ↔ ↓ ↑ ↑ ↔ ↓ ↔ ↓ ↓
Glucagon-like
peptide 1 level
↔ ↓ ↔ ↔
Peptide YY level ↑ ↔ ↔ ↔
Cholecystokinin
level
↔ ↓
Leptin level ↓ ↓ ↔ ↓
Adiponectin level ↔ ↔ ↑
Bile acids ↑ ↓ ↑
Gut microbiota Gene richness ↑ ↓;
Proteobacteria ↑
E. Coli ↑;
Eubacterium
rectale ↓;
Roseburia
intestinalis ↓
Eating habit Binge eating ↔ ↓;
emotional eating ↔ ↓;
night eating ↓;
grazing ↑
High-caloric food ↑;
sweet food ↑;
vegetable↓; fruit ↓
Grazing ↓;
emotional eating ↓;
sweet food ↓;
after-dinner grazing ↓
↑, increased; ↔, unchanged; ↓, decreased. More than one arrow indicates inconsistent data; blank means unknown data.
Chang et al., 2021). Furthermore, gastric clip has been used to
assist with SG, but a gastrectomy was still performed to achieve
metabolic improvements in mice (Schlager et al., 2011;Wei et al.,
2020). This implies that a simple gastric clip may not be a reliable
bariatric device as a stand-alone. More follow-up data is needed.
Intragastric Balloons
Intragastric balloons (IGB) have been used to occupy the
gastric space by endoscopic placement as shown in Figure 1C.
The FDA has approved three IGBs (Vyas et al., 2017;Vargas
et al., 2018), i.e., Orbera, Obalon, and ReShape Duo [no
longer available (FDA, 2020)] to combat obesity with BMI
30–40 kg/m2. In addition, there have been some other IGBs
(such as Elipse, Medsil, Spatz3, and so on) (Bužga et al.,
2014;Ramai et al., 2020;Badurdeen et al., 2021) awaiting for
validation or approval. As a result, reducing gastric capacity
via endoscopically implanted IGBs has emerged as a viable
option to alleviate morbid obesity. A retrospective study of
5,874 patients (Fittipaldi-Fernandez et al., 2020) showed that
the incidence of gastric perforation and digestive bleeding were
only 0.07 and 0.05% in the first half year after IGB implant.
According to the American Society for Metabolic and Bariatric
Surgery (2021), in 2015, balloons were used only in 0.3% cases
of bariatric procedures in the US, while in 2019 the number
increased to 1.8%.
Generally, the balloons are placed endoscopically into
stomach for no more than 6 months (in some techniques the
time is longer), after which they are removed. A meta-analysis
including 5,668 subjects (Popov et al., 2017) reported that
patients had 28% excess weight loss and 4.8 kg/m2BMI decrease
at 6 months after IGBs removal, although some weight regain
was observed at balloon removal. Some investigators showed that
after 6-month implantation, the total weight loss of the IGBs
is 6.8–13.2% (Vargas et al., 2018); at 12 months, i.e., 6 months
following balloon removal, the weight loss is still satisfactory,
albeit modest at 7.6–11.3% total weight loss (Vargas et al., 2018).
This indicates that the weight reduction outcome after IGBs is
not dependent on gastric restriction. Genco et al. (2013) reported
that IGB placement improves eating habits, reducing frequent
food consuming, preference of sweet foods, emotional eating,
and after-dinner grazing in patients with obesity. Some IGBs
are reported to alter gastric motility and hormone levels in
addition to reducing gastric volume. Mion et al. (2005) found
that balloon placement leads to suppression of gastric emptying
and ghrelin production, but the subsequent weight reduction is
not associated with gastric emptying. Another study (Mathus-
Vliegen and de Groot, 2013) reported a decrease of CCK after
IGBs, which may correlate with delayed gastric emptying. In
these studies, the variations of ghrelin and CCK are likely to be
the results of weight loss rather than the causes. Fuller’s group
(Fuller et al., 2013) performed a randomized controlled trial
for IGB evaluation. In their study, ghrelin was increased and
leptin was decreased when the device was implanted, but both
concentrations recovered to baseline after the removal of the
balloon. In addition, fasting levels of adiponectin or Peptide YY
(PYY) were not affected by weight loss associated with the IGBs
treatment. Similarly, Bužga et al. (2014) observed that serum
ghrelin was increased while leptin and fibroblast growth factor
21 levels were decreased at 6 months after balloon insertion in
patients with BMI of 43 kg/m2, but longer-term results were
Frontiers in Physiology | www.frontiersin.org 4October 2021 | Volume 12 | Article 761481

fphys-12-761481 October 22, 2021 Time: 14:39 # 5
Wang and Kassab Mechanisms Underlying Restrictive Devices
not assessed. Another study (Mathus-Vliegen and Eichenberger,
2014) also indicated that fasting and postprandial ghrelin levels
remained stable at 13 and 26 weeks after IGBs, despite sustained
weight loss. A study (Badurdeen et al., 2021) showed that 9-
month administration of Liraglutide (GLP-1 agonist) after IGB
removal was effective in preventing weight regain and reducing
fat mass. It indicates that GLP-1 concentration is potentially
an important factor of IGB-induced weight loss, which needs
further verification.
Aside from the potential changes in gastrointestinal motility
and hormones, IGB therapy reduces fat mass and resting
metabolic rate (Ga´
zdzi´
nska et al., 2020), which are associated
with weight decrease. IGBs are also reported to improve
obesity related disorders such as hypertension (Popov et al.,
2017), hyperglycemia (Popov et al., 2017), dyslipidemia
(Ramai et al., 2020), and non-alcoholic fatty liver disease
(Chandan et al., 2021). More studies are needed to reveal
deeper mechanisms.
Endoscopic Gastroplasty and
Gastroplication
Endoscopic Sleeve Gastroplasty (ESG) is also an emerging
endoluminal method to manage obesity. First used in patients
a decade ago, it has been improved in recent years (Kumar
et al., 2018). Using endoscopic suturing devices, ESG procedure
places a series of sutures from the antrum to the fundus,
creating a banana-shape stomach pouch like SG does. Similar
devices to mimic SG or gastroplasty include Apollo OverStitch,
EndoCinch, Incisionless Operating Platform, amongst others
(Kumar, 2015).
In comparison of laparoscopic SG and AGB, although SG
achieved the greatest weight reduction, ESG is thought to be
the safest and most viable choice with lower morbidity and
shorter stay in hospital (Novikov et al., 2018). Jain et al.
(2017) summarized nine single center prospective human studies
treating obesity by ESG technique. In these studies, no intra-
procedure complication was reported, while 2.3% of the patients
experienced major but not fatal postoperative complications such
as perigastric leakage. Although the detailed techniques were
different, the % excess weight loss was reported to be 30–57
(Jain et al., 2017). An international multicenter study (Barrichello
et al., 2019) showed that at 12-month after ESG, the total and
excess weight loss were 15.1 and 59.4%, and adipose tissue was
significantly lowered. Lopez-Nava and coworkers retrospectively
analyzed 248 patients, indicating that at 6 and 24 months after
ESG, the total weight loss was 15.2 and 18.6%, respectively
(Lopez-Nava et al., 2017). In another study with a smaller group
of patients, they found that at 1 year after ESG, BMI loss
was 7.3 kg/m2, while total and excess weight loss were 18.7
and 54.6% (Lopez-Nava et al., 2016). Alqahtani et al. (2019)
provided similar data, showing 13.7, 15, and 14.8% total weight
loss at 6, 12, 18 months, respectively. In this study, ESG also
resulted in satisfactory remissions of diabetes, hypertension, and
dyslipidemia (Alqahtani et al., 2019). Sharaiha et al. (2017)
studied 91 consecutive patients who underwent ESG. At 1 year
after procedure, the patients not only lost 14.4% body weight,
but also showed significantly improved levels of hemoglobin A1c,
systolic blood pressure, alanine aminotransferase, and serum
triglycerides (Sharaiha et al., 2017).
There have been some studies exploring the underlying
contributors of weight loss and metabolic improvements beyond
restriction following ESG. Lopez-Nava et al. (2020) found a
reduced levels of leptin and an improved insulin secretory pattern
in patients at 6 months after ESG, while ghrelin, GLP-1, PYY,
and adiponectin remained stable. These changes differed from
those following SG, which is likely because of the different post-
operatively anatomical structures between the two procedures.
The researchers concluded that hormonal variations play little
role in weight loss and metabolic improvements (Lopez-Nava
et al., 2020). In contrast, Abu Dayyeh et al. (2017) revealed
that insulin sensitivity was improved after ESG, with decreased
(not significantly) ghrelin levels and unchanged leptin, GLP-
1, and PYY. Moreover, they reported that ESG delays gastric
emptying, thus producing early satiation and decreasing caloric
consumption to reach maximum fullness in patients, but the
sample size was to be increased (Abu Dayyeh et al., 2017).
This finding is in support of the above-mentioned Lopez-Nava
et al.’s conclusion, although the gut hormone changes in the two
papers were not comparable. The variation may mainly be due
to different follow-up duration as well as baseline conditions
of the subjects.
The articulating circular endoscopic (ACE) stapler is a
transoral bariatric device for endoscopic gastroplication which
has identical principle to ESG. Paulus et al. (2020) reported that
in subjects whose BMI was 38.3 kg/m2at baseline, BMI decreased
to 33.9 kg/m2at 1 year postoperatively. After the procedure,
patients had a downregulated ghrelin gene expression as well
as its activating enzyme in the upper gastrointestinal tract and
increased level of plasma adiponectin (van der Wielen et al.,
2017). Trans-oral endoscopic restrictive implant system (De Jong
et al., 2010;Verlaan et al., 2016) is another similar device. At
6 months after using the device, total and excess weight loss were
15.1 and 30.1%, but the longer-term effects were not reported yet
and the biological mediators were to be explored.
Other Bariatric Technologies
It should be noted that there are other bariatric devices than we
could include in the rapidly developing field, and every technique
has both the pros and cons. Our current review mainly focuses
on mechanisms behind the gastric volume restricted devices.
Understanding the possible mechanisms beyond restriction will
help us better understand the pathophysiology of obesity and
provide the potential to develop more effective approaches to
combat the epidemic of obesity. Table 1 summarizes the factors
that may contribute to weight control with device implants.
CONCLUSION
Although many gastric volume-restriction bariatric devices have
been developed for laboratory or clinical use, the underlying
mechanism of the devices in alleviating morbid obesity and
comorbidities is still not fully understood. Despite the fact that
Frontiers in Physiology | www.frontiersin.org 5October 2021 | Volume 12 | Article 761481

fphys-12-761481 October 22, 2021 Time: 14:39 # 6
Wang and Kassab Mechanisms Underlying Restrictive Devices
the “restrictive” devices physically limit or reduce gastric
capacity, mechanical restriction may not have the key role
in achieving the beneficial outcomes. Gastric motility and
hormone responses may also contribute to the efficacy of
the procedures. Changes in hormone levels provide some
indication as to how these bariatric devices work; however,
they do not necessarily provide a mechanism for the weight
loss effects. Instead, these changes could be compensatory,
rather than mediators. Further studies are required to determine
whether these changes in hormone levels are in fact causal
to weight loss. Studies regarding other factors that contribute
to bariatric surgeries (Madsbad et al., 2014;Wang et al., 2019)
such as vagal and hypothalamic activity, role of bile acids,
and gut flora alterations are lacking. More studies are
encouraged to elucidate the detailed mechanisms of weight and
energy regulation and glucose metabolism after use of gastric
bariatric devices.
AUTHOR CONTRIBUTIONS
YW searched and arranged literatures. GK engaged in the
conception, design, and coordination of the work. Both authors
participated in drafting and revising the manuscript.
REFERENCES
Abu Dayyeh, B. K., Acosta, A., Camilleri, M., Mundi, M. S., Rajan, E., Topazian,
M. D., et al. (2017). Endoscopic sleeve gastroplasty alters gastric physiology and
induces loss of body weight in obese individuals. Clin. Gastroenterol. Hepatol.
15, 37–43.e1. doi: 10.1016/j.cgh.2015.12.030
Alqahtani, A., Al-Darwish, A., Mahmoud, A. E., Alqahtani, Y. A., and Elahmedi,
M. (2019). Short-term outcomes of endoscopic sleeve gastroplasty in 1000
consecutive patients. Gastrointest. Endosc. 89, 1132–1138. doi: 10.1016/j.gie.
2018.12.012
American Society for Metabolic and Bariatric Surgery (2021). Estimate of Bariatric
Surgery Numbers, 2011-2019. Available Online at: https://asmbs.org/resources/
estimate-of- bariatric-surgery-numbers (accessed March 30, 2021).
Amsalem, D., Aricha-Tamir, B., Levi, I., Shai, D., and Sheiner, E. (2014). Obstetric
outcomes after restrictive bariatric surgery: what happens after 2 consecutive
pregnancies? Surg. Obes. Relat. Dis. 10, 445–449. doi: 10.1016/j.soard.2013.08.
016
Arias, I. E., Radulescu, M., Stiegeler, R., Singh, J. P., Martinez, P., Ramirez, A.,
et al. (2009). Diagnosis and treatment of megaesophagus after adjustable gastric
banding for morbid obesity. Surg. Obes. Relat. Dis. 5, 156–159. doi: 10.1016/j.
soard.2008.11.007
Aron-Wisnewsky, J., Prifti, E., Belda, E., Ichou, F., Kayser, B. D., Dao, M. C., et al.
(2019). Major microbiota dysbiosis in severe obesity: fate after bariatric surgery.
Gut 68, 70–82. doi: 10.1136/gutjnl-2018-316103
Badurdeen, D., Hoff, A. C., Barrichello, S., Hedjoudje, A., Itani, M. I., Farha, J.,
et al. (2021). Efficacy of liraglutide to prevent weight regain after retrieval
of an adjustable intra-gastric balloon—a case-matched study. Obes. Surg. 31,
1204–1213. doi: 10.1007/s11695-020-05117- 8
Balsiger, B. M., Poggio, J. L., Mai, J., Kelly, K. A., and Sarr, M. G. (2000). Ten and
more years after vertical banded gastroplasty as primary operation for morbid
obesity. J. Gastrointest. Surg. 4, 598–605. doi: 10.1016/S1091-255X(00)80108-0
Barrichello, S., Hourneaux, de Moura, D. T., Hourneaux de Moura, E. G., Jirapinyo,
P., Hoff, A. C., et al. (2019). Endoscopic sleeve gastroplasty in the management
of overweight and obesity: an international multicenter study. Gastrointest.
Endosc. 90, 770–780. doi: 10.1016/j.gie.2019.06.013
Bentham, J., Di Cesare, M., Bilano, V., Bixby, H., Zhou, B., Stevens, G. A.,
et al. (2017). Worldwide trends in body-mass index, underweight, overweight,
and obesity from 1975 to 2016: a pooled analysis of 2416 population-based
measurement studies in 128·9 million children, adolescents, and adults. Lancet
390, 2627–2642. doi: 10.1016/S0140-6736(17)32129-3
Billy, H. T., Sarwer, D. B., Ponce, J., Ng-Mak, D. S., Shi, R., Cornell, C., et al.
(2014). Quality of life after laparoscopic adjustable gastric banding (LAP-
BAND): APEX interim 3-year analysis. Postgrad. Med. 126, 131–140. doi:
10.3810/pgm.2014.07.2791
Brolin, R. E., Robertson, L. B., Kenler, H. A., and Cody, R. P. (1994). Weight loss
and dietary intake after vertical banded gastroplasty and Roux-en-Y gastric
bypass. Ann. Surg. 220, 782–790. doi: 10.1097/00000658-199412000-00012
Bužga, M., Machytka, E., Klvaˇ
na, P., Kupka, T., Zavadilová, V., Zonˇ
ca, P., et al.
(2014). Effects of the intragastric balloon Medsil R
on weight loss, fat tissue, lipid
metabolism, and hormones involved in energy balance. Obes. Surg. 24, 909–915.
doi: 10.1007/s11695-014- 1191-4
Chandan, S., Mohan, B. P., Khan, S. R., Facciorusso, A., Ramai, D., Kassab, L. L.,
et al. (2021). Efficacy and safety of intragastric balloon (IGB) in non-alcoholic
fatty liver disease (NAFLD): a comprehensive review and meta-analysis. Obes.
Surg. 31, 1271–1279. doi: 10.1007/s11695-020-05084- 0
Chang, P.-C., Chen, K.-H., Huang, I. Y.-W., Huang, C.-K., Chen, C.-Y., Wang,
M.-Y., et al. (2021). Laparoscopic revision for gastric clipping: a single center
experience and taiwan database review. Obes. Surg. 31, 3653–3659. doi: 10.
1007/s11695-021-05466-y
Chang, S.-H., Stoll, C. R. T., Song, J., Varela, J. E., Eagon, C. J., and Colditz, G. A.
(2014). The effectiveness and risks of bariatric surgery: an updated systematic
review and meta-analysis, 2003-2012. JAMA Surg. 149, 275–287. doi: 10.1001/
jamasurg.2013.3654
Chao, S. H., Lin, C. L., Lee, W. J., Chen, J. C., and Chou, J. J. (2019). Proximal
jejunal bypass improves the outcome of gastric clip in patients with obesity and
type 2 diabetes mellitus. Obes. Surg. 29, 1148–1153. doi: 10.1007/s11695-018-3
607-z
De Jong, K., Mathus-Vliegen, E. M. H., Veldhuyzen, E. A. M. L., Eshuis, J. H., and
Fockens, P. (2010). Short-term safety and efficacy of the trans-oral endoscopic
restrictive implant system for the treatment of obesity. Gastrointest. Endosc. 72,
497–504. doi: 10.1016/j.gie.2010.02.053
de la Plaza Llamas, R., Díaz Candelas, D. A., and Ramia, J. M. (2020). Laparoscopic
removal of a displaced vertical gastric clip causing gastric outlet obstruction.
Obes. Surg. 30, 2856–2857. doi: 10.1007/s11695-020-04606-0
Doble, B., Welbourn, R., Carter, N., Byrne, J., Rogers, C. A., Blazeby, J. M.,
et al. (2019). Multi-Centre micro-costing of Roux-En-Y gastric bypass, sleeve
gastrectomy and adjustable gastric banding procedures for the treatment of
severe, complex obesity. Obes. Surg. 29, 474–484. doi: 10.1007/s11695-018-
3553-9
Edelman, S., Ng-Mak, D. S., Fusco, M., Ashton, D., Okerson, T., Liu, Q., et al.
(2014). Control of type 2 diabetes after 1 year of laparoscopic adjustable gastric
banding in the helping evaluate reduction in obesity (HERO) study. Diabetes,
Obes. Metab. 16, 1009–1015. doi: 10.1111/dom.12313
Favretti, F., Ashton, D., Busetto, L., Segato, G., and De Luca, M. (2009). The gastric
band: first-choice procedure for obesity surgery. World J. Surg. 33, 2039–2048.
doi: 10.1007/s00268-009- 0091-6
FDA (2020). UPDATE: Potential Risks with Liquid-filled Intragastric Balloons -
Letter to Health Care Providers | FDA. AvailableOnline at: https://www.fda.gov/
medical-devices/letters- health-care- providers/update-potential- risks-liquid-
filled-intragastric- balloons-letter-health-care-providers-0 (accessed March 22,
2021).
Fittipaldi-Fernandez, R. J., Zotarelli-Filho, I. J., Diestel, C. F., Klein, M. R. S. T.,
de Santana, M. F., de Lima, J. H. F., et al. (2020). Intragastric balloon: a
retrospective evaluation of 5874 patients on tolerance, complications, and
efficacy in different degrees of overweight. Obes. Surg. 30, 4892–4898. doi:
10.1007/s11695-020-04985-4
Flegal, K. M., Carroll, M. D., Kit, B. K., and Ogden, C. L. (2012). Prevalence of
obesity and trends in the distribution of body mass index among US adults,
1999-2010. JAMA 307, 491–497. doi: 10.1001/jama.2012.39
Froylich, D., Abramovich, T. S., Fuchs, S., Zippel, D., and Hazzan, D. (2020). Long-
term (over 13 years) follow-up of vertical band gastroplasty. Obes. Surg. 30,
1808–1813. doi: 10.1007/s11695-020-04448- w
Frontiers in Physiology | www.frontiersin.org 6October 2021 | Volume 12 | Article 761481

fphys-12-761481 October 22, 2021 Time: 14:39 # 7
Wang and Kassab Mechanisms Underlying Restrictive Devices
Fuller, N. R., Lau, N. S., Denyer, G., and Caterson, I. D. (2013). An intragastric
balloon produces large weight losses in the absence of a change in ghrelin or
peptide YY. Clin. Obes. 3, 172–179. doi: 10.1111/cob.12030
Garb, J., Welch, G., Zagarins, S., Kuhn, J., and Romanelli, J. (2009). Bariatric
surgery for the treatment of morbid obesity: a meta-analysis of weight loss
outcomes for laparoscopic adjustable gastric banding and laparoscopic gastric
bypass. Obes. Surg. 19, 1447–1455. doi: 10.1007/s11695-009-9927- 2
Gasoyan, H., Tajeu, G., Halpern, M. T., and Sarwer, D. B. (2019). Reasons for
underutilization of bariatric surgery: the role of insurance benefit design. Surg.
Obes. Relat. Dis. 15, 146–151. doi: 10.1016/j.soard.2018.10.005
Ga´
zdzi´
nska, A. P., Mojkowska, A., Zieli´
nski, P., and Gazdzinski, S. P. (2020).
Changes in resting metabolic rate and body composition due to intragastric
balloon therapy. Surg. Obes. Relat. Dis. 16, 34–39. doi: 10.1016/j.soard.2019.
10.011
Genco, A., Maselli, R., Frangella, F., Cipriano, M., Paone, E., Meuti, V., et al. (2013).
Effect of consecutive intragastric balloon (BIB R
) plus diet versus single BIB R

plus diet on eating disorders not otherwise specified (EDNOS) in obese patients.
Obes. Surg. 23, 2075–2079. doi: 10.1007/s11695-013-1028- 6
Golzarand, M., Toolabi, K., and Farid, R. (2017). The bariatric surgery and
weight losing: a meta-analysis in the long- and very long-term effects of
laparoscopic adjustable gastric banding, laparoscopic Roux-en-Y gastric bypass
and laparoscopic sleeve gastrectomy on weight loss in adults. Surg. Endosc. 31,
4331–4345. doi: 10.1007/s00464-017-5505- 1
Guo, X., Mattar, S. G., Mimms, S. E., Navia, J. A., and Kassab, G. S. (2014). Efficacy
of a laparoscopic gastric restrictive device in an obese canine model. Obes. Surg.
24, 159–166. doi: 10.1007/s11695-013-1127- 4
Guo, X., Mattar, S. G., Navia, J. A., and Kassab, G. S. (2012). Response of gut
hormones after implantation of a reversible gastric restrictive device in different
animal models. J. Surg. Res. 178, 165–171. doi: 10.1016/j.jss.2012.02.032
Guo, X., Zheng, H., Mattar, S. G., Lu, X., Sandusky, G., Navia, J. A., et al. (2011).
Reversible gastric restriction implant: safety and efficacy in a canine model.
Obes. Surg. 21, 1444–1450. doi: 10.1007/s11695-010-0299- 4
Hindle, A., Garcia, X. D. P., Hayden, M., O’Brien, P. E., and Brennan, L. (2020).
Pre-operative restraint and post-operative hunger, disinhibition and emotional
eating predict weight loss at 2 Years post-laparoscopic adjustable gastric
banding. Obes. Surg. 30, 1347–1359. doi: 10.1007/s11695-019-04274- 9
Ibrahim, A. M., Thumma, J. R., and Dimick, J. B. (2017). Reoperation and medicare
expenditures after laparoscopic gastric band surgery. JAMA Surg. 152, 835–842.
doi: 10.1001/jamasurg.2017.1093
Jacobs, M., Zundel, N., Plasencia, G., Rodriguez-Pumarol, P., Gomez, E., and
Leithead, J. (2017). A vertically placed clip for weight loss: a 39-month pilot
study. Obes. Surg. 27, 1174–1181. doi: 10.1007/s11695-016-2432- 5
Jain, D., Bhandari, B. S., Arora, A., and Singhal, S. (2017). Endoscopic sleeve
gastroplasty - a New tool to manage obesity. Clin. Endosc. 50, 552–561. doi:
10.5946/ce.2017.032
Jensen, M. D., Ryan, D. H., Apovian, C. M., Ard, J. D., Comuzzie, A. G., Donato,
K. A., et al. (2014). 2013 AHA/ACC/TOS guideline for the management
of overweight and obesity in adults: a report of the American college of
cardiology/American heart association task force on practice guidelines and the
obesity society. J. Am. Coll. Cardiol. 63, 2985–3023. doi: 10.1016/j.jacc.2013.11.
004
Kawasaki, T., Ohta, M., Kawano, Y., Masuda, T., Gotoh, K., Inomata, M., et al.
(2015). Effects of sleeve gastrectomy and gastric banding on the hypothalamic
feeding center in an obese rat model. Surg. Today 45, 1560–1566. doi: 10.1007/
s00595-015-1135-1
Kellum, J. M., Kuemmerle, J. F., O’Dorisio, T. M., Rayford, P., Martin, D., Engle,
K., et al. (1990). Gastrointestinal hormone responses to meals before and after
gastric bypass and vertical banded gastroplasty. Ann. Surg. 211, 763–771. doi:
10.1097/00000658-199006000-00016
Kodner, C., and Hartman, D. R. (2014). Complications of adjustable gastric
banding surgery for obesity. Am. Fam. Physician 89, 813–818.
Kumar, N. (2015). Endoscopic therapy for weight loss: gastroplasty, duodenal
sleeves, intragastric balloons, and aspiration. World J. Gastrointest. Endosc. 7,
847–859. doi: 10.4253/wjge.v7.i9.847
Kumar, N., Abu Dayyeh, B. K., Lopez-Nava Breviere, G., Galvao Neto, M. P.,
Sahdala, N. P., Shaikh, S. N., et al. (2018). Endoscopic sutured gastroplasty:
procedure evolution from first-in-man cases through current technique. Surg.
Endosc. 32, 2159–2164. doi: 10.1007/s00464-017-5869- 2
Kuzmak, L. I. (1991). A review of seven years’ experience with silicone gastric
banding. Obes. Surg. Incl. Laparosc. Allied Care 1, 403–408. doi: 10.1381/
096089291765560809
Lee, C. J., Florea, L., Sears, C. L., Maruthur, N., Potter, J. J., Schweitzer, M.,
et al. (2019). Changes in gut microbiome after bariatric surgery versus medical
weight loss in a pilot randomized trial. Obes. Surg. 29, 3239–3245. doi: 10.1007/
s11695-019-03976-4
Leonetti, F., Silecchia, G., Iacobellis, G., Ribaudo, M. C., Zappaterreno, A., Tiberti,
C., et al. (2003). Different plasma ghrelin levels after laparoscopic gastric bypass
and adjustable gastric banding in morbid obese subjects. J. Clin. Endocrinol.
Metab. 88, 4227–4231. doi: 10.1210/jc.2003-030133
Lopez-Nava, G., Galvao, M., Bautista-Castaño, I., Fernandez-Corbelle, J., and
Trell, M. (2016). Endoscopic sleeve gastroplasty with 1-year follow-up: factors
predictive of success. Endosc. Int. Open 04, E222–E227. doi: 10.1055/s-0041-
110771
Lopez-Nava, G., Negi, A., Bautista-Castaño, I., Rubio, M. A., and Asokkumar,
R. (2020). Gut and metabolic hormones changes after endoscopic sleeve
gastroplasty (ESG) vs. laparoscopic sleeve gastrectomy (LSG). Obes. Surg. 30,
2642–2651. doi: 10.1007/s11695-020-04541- 0
Lopez-Nava, G., Sharaiha, R. Z., Vargas, E. J., Bazerbachi, F., Manoel, G. N.,
Bautista-Castaño, I., et al. (2017). Endoscopic sleeve gastroplasty for obesity:
a multicenter study of 248 patients with 24 months follow-up. Obes. Surg. 27,
2649–2655. doi: 10.1007/s11695-017-2693- 7
Madsbad, S., Dirksen, C., and Holst, J. J. (2014). Mechanisms of changes in glucose
metabolism and bodyweight after bariatric surgery. lancet. Diabetes Endocrinol.
2, 152–164. doi: 10.1016/S2213-8587(13)70218-3
Mason, E. E. (1982). Vertical banded gastroplasty for obesity. Arch. Surg. 117,
701–706. doi: 10.1001/archsurg.1982.01380290147026
Mathus-Vliegen, E. M. H., and de Groot, G. H. (2013). Fasting and meal-induced
CCK and PP secretion following intragastric balloon treatment for obesity.
Obes. Surg. 23, 622–633. doi: 10.1007/s11695-012-0834- 6
Mathus-Vliegen, E. M. H., and Eichenberger, R. I. (2014). Fasting and meal-
suppressed ghrelin levels before and after intragastric balloons and balloon-
induced weight loss. Obes. Surg. 24, 85–94. doi: 10.1007/s11695-013-1
053-5
Mion, F., Napoléon, B., Roman, S., Malvoisin, E., Trepo, F., Pujol, B., et al.
(2005). Effects of intragastric balloon on gastric emptying and plasma ghrelin
levels in non-morbid obese patients. Obes. Surg. 15, 510–516. doi: 10.1381/
0960892053723411
Monteiro, M. P., Ribeiro, A. H., Nunes, A. F., Sousa, M. M., Monteiro, J. D.,
Águas, A. P., et al. (2007). Increase in ghrelin levels after weight loss in obese
Zucker rats is prevented by gastric banding. Obes. Surg. 17, 1599–1607. doi:
10.1007/s11695-007-9324-7
Noel, P., Eddbali, I., and Nedelcu, M. (2020). Laparoscopic clip gastroplasty
with the BariClip. Obes. Surg. 30, 5182–5183. doi: 10.1007/s11695-020-04
803-x
Noel, P., Nedelcu, A. M., Eddbali, I., and Zundel, N. (2018). Laparoscopic vertical
clip gastroplasty - quality of life. Surg. Obes. Relat. Dis. 14, 1587–1593. doi:
10.1016/j.soard.2018.07.013
Novikov, A. A., Afaneh, C., Saumoy, M., Parra, V., Shukla, A., Dakin, G. F., et al.
(2018). Endoscopic sleeve gastroplasty, laparoscopic sleeve gastrectomy, and
laparoscopic band for weight loss: how do they compare? J. Gastrointest. Surg.
22, 267–273. doi: 10.1007/s11605-017-3615- 7
Ogden, C. L., Carroll, M. D., Lawman, H. G., Fryar, C. D., Kruszon-Moran, D., Kit,
B. K., et al. (2016). Trends in obesity prevalence among children and adolescents
in the United States, 1988-1994 through 2013-2014. JAMA 315, 2292–2299.
doi: 10.1001/jama.2016.6361
Olbers, T., Björkman, S., Lindroos, A., Maleckas, A., Lönn, L., Sjöström, L.,
et al. (2006). Body composition, dietary intake, and energy expenditure
after laparoscopic Roux-en-Y gastric bypass and laparoscopic vertical banded
gastroplasty: a randomized clinical trial. Ann. Surg. 244, 715–722. doi: 10.1097/
01.sla.0000218085.25902.f8
Opozda, M., Chur-Hansen, A., and Wittert, G. (2016). Changes in problematic and
disordered eating after gastric bypass, adjustable gastric banding and vertical
sleeve gastrectomy: a systematic review of pre-post studies. Obes. Rev. 17,
770–792. doi: 10.1111/obr.12425
Park, C. H., Nam, S.-J., Choi, H. S., Kim, K. O., Kim, D. H., Kim, J.-W., et al. (2019).
Comparative efficacy of bariatric surgery in the treatment of morbid obesity and
Frontiers in Physiology | www.frontiersin.org 7October 2021 | Volume 12 | Article 761481

fphys-12-761481 October 22, 2021 Time: 14:39 # 8
Wang and Kassab Mechanisms Underlying Restrictive Devices
diabetes mellitus: a systematic review and network meta-analysis. Obes. Surg.
29, 2180–2190. doi: 10.1007/s11695-019-03831- 6
Paulus, G. F., van Avesaat, M., Crijnen, J. A. W., Ernest, van Heurn, L. W.,
Westerterp-Plantenga, M. S., et al. (2020). Preliminary evidence that endoscopic
gastroplication reduces food reward. Appetite 150:104632. doi: 10.1016/j.appet.
2020.104632
Ponce, J., Taheri, S., Lusco, V., Cornell, C., Ng-Mak, D. S., Shi, R., et al. (2014).
Efficacy and safety of the adjustable gastric band-pooled interim analysis of
the APEX and HERO studies at 48 weeks. Curr. Med. Res. Opin. 30, 841–848.
doi: 10.1185/03007995.2013.874992
Pontiroli, A. E., Zakaria, A. S., Fanchini, M., Osio, C., Tagliabue, E., Micheletto,
G., et al. (2018). A 23-year study of mortality and development of co-
morbidities in patients with obesity undergoing bariatric surgery (laparoscopic
gastric banding) in comparison with medical treatment of obesity. Cardiovasc.
Diabetol. 17:161. doi: 10.1186/s12933-018-0801-1
Popov, V. B., Ou, A., Schulman, A. R., and Thompson, C. C. (2017). The impact of
intragastric balloons on obesity-related co-morbidities: a systematic review and
meta-analysis. Am. J. Gastroenterol. 112, 429–439. doi: 10.1038/ajg.2016.530
Pournaras, D. J., Osborne, A., Hawkins, S. C., Vincent, R. P., Mahon, D., Ewings,
P., et al. (2010). Remission of type 2 diabetes after gastric bypass and banding:
mechanisms and 2 year outcomes. Ann. Surg. 252, 966–971. doi: 10.1097/SLA.
0b013e3181efc49a
Ramai, D., Singh, J., Mohan, B. P., Madedor, O., Brooks, O. W., Barakat, M., et al.
(2020). Influence of the elipse intragastric balloon on obesity and metabolic
profile: a systematic review and meta-analysis. J. Clin. Gastroenterol. online
ahead of print. doi: 10.1097/MCG.0000000000001484
Schlager, A., Khalaileh, A., Mintz, Y., Gazala, M. A., Globerman, A., Ilani,
N., et al. (2011). A mouse model for sleeve gastrectomy: applications
for diabetes research. Microsurgery 31, 66–71. doi: 10.1002/micr.2
0797
Sharaiha, R. Z., Kumta, N. A., Saumoy, M., Desai, A. P., Sarkisian, A. M.,
Benevenuto, A., et al. (2017). Endoscopic sleeve gastroplasty significantly
reduces body mass index and metabolic complications in obese patients. Clin.
Gastroenterol. Hepatol. 15, 504–510. doi: 10.1016/j.cgh.2016.12.012
Smith, K. E., Orcutt, M., Steffen, K. J., Crosby, R. D., Cao, L., Garcia, L., et al. (2019).
Loss of control eating and binge eating in the 7 years following bariatric surgery.
Obes. Surg. 29, 1773–1780. doi: 10.1007/s11695- 019-03791-x
Sonavane, S. K., Menias, C. O., Kantawala, K. P., Shanbhogue, A. K., Prasad,
S. R., Eagon, J. C., et al. (2012). Laparoscopic adjustable gastric banding:
what radiologists need to know. Radiographics 32, 1161–1178. doi: 10.1148/
rg.324115177
Sysko, R., Devlin, M. J., Schebendach, J., Tanofsky-Kraff, M., Zimmerli, E., Korner,
J., et al. (2013). Hormonal responses and test meal intake among obese teenagers
before and after laparoscopic adjustable gastric banding. Am. J. Clin. Nutr. 98,
1151–1161. doi: 10.3945/ajcn.113.061762
Tremaroli, V., Karlsson, F., Werling, M., Ståhlman, M., Kovatcheva-Datchary,
P., Olbers, T., et al. (2015). Roux-en-Y gastric bypass and vertical banded
gastroplasty induce long-Term changes on the human gut microbiome
contributing to fat mass regulation. Cell Metab. 22, 228–238. doi: 10.1016/j.
cmet.2015.07.009
Tsai, C., Zehetner, J., Beel, J., and Steffen, R. (2019). Long-term outcomes and
frequency of reoperative bariatric surgery beyond 15 years after gastric banding:
a high band failure rate with safe revisions. Surg. Obes. Relat. Dis. 15, 900–907.
doi: 10.1016/j.soard.2019.03.017
van der Wielen, N., Paulus, G., van Avesaat, M., Masclee, A., Meijerink, J., and
Bouvy, N. (2017). Effect of endoscopic gastroplication on the genome-wide
transcriptome in the upper gastrointestinal tract. Obes. Surg. 27, 740–748. doi:
10.1007/s11695-016-2356-0
van Wezenbeek, M. R., Smulders, J. F., de Zoete, J. P. J. G. M., Luyer, M. D.,
van Montfort, G., and Nienhuijs, S. W. (2015). Long-term results of primary
vertical banded gastroplasty. Obes. Surg. 25, 1425–1430. doi: 10.1007/s11695-
014-1543-0
Vargas, E. J., Rizk, M., Bazerbachi, F., and Abu Dayyeh, B. K. (2018). Medical
devices for obesity treatment: endoscopic bariatric therapies. Med. Clin. North
Am. 102, 149–163. doi: 10.1016/j.mcna.2017.08.013
Verlaan, T., de Jong, K., de la Mar-Ploem, E. D., Veldhuyzen, E. A., Mathus-
Vliegen, E. M., and Fockens, P. (2016). Trans-oral endoscopic restrictive
implant system: endoscopic treatment of obesity? Surg. Obes. Relat. Dis. 12,
1711–1718. doi: 10.1016/j.soard.2016.02.027
Vyas, D., Deshpande, K., and Pandya, Y. (2017). Advances in endoscopic balloon
therapy for weight loss and its limitations. World J. Gastroenterol. 23, 7813–
7817. doi: 10.3748/wjg.v23.i44.7813
Wang, Y., Guo, X., Lu, X., Mattar, S., and Kassab, G. (2019). Mechanisms of weight
loss after sleeve gastrectomy and adjustable gastric banding: far more than just
restriction. Obesity 27, 1776–1783. doi: 10.1002/oby.22623
Wei, J.-H., Yeh, C.-H., Lee, W.-J., Lin, S.-J., and Huang, P.-H. (2020). Sleeve
gastrectomy in mice using surgical clips. J. Vis. Exp., e60719. doi: 10.3791/60719
Wharton, S., Lau, D. C. W., Vallis, E. M., Sharma, A. M., Biertho, L., Campbell-
Scherer, D., et al. (2020). Obesity in adults: a clinical practice guideline. CMAJ
192, E875–E891. doi: 10.1503/cmaj.191707
Yumuk, V., Tsigos, C., Fried, M., Schindler, K., Busetto, L., Micic, D., et al. (2015).
European guidelines for obesity management in adults. Obes. Facts 8, 402–424.
doi: 10.1159/000442721
Conflict of Interest: The authors declare that the research was conducted in the
absence of any commercial or financial relationships that could be construed as a
potential conflict of interest.
Publisher’s Note: All claims expressed in this article are solely those of the authors
and do not necessarily represent those of their affiliated organizations, or those of
the publisher, the editors and the reviewers. Any product that may be evaluated in
this article, or claim that may be made by its manufacturer, is not guaranteed or
endorsed by the publisher.
Copyright © 2021 Wang and Kassab. This is an open-access article distributed
under the terms of the Creative Commons Attribution License (CC BY). The use,
distribution or reproduction in other forums is permitted, provided the original
author(s) and the copyright owner(s) are credited and that the original publication
in this journal is cited, in accordance with accepted academic practice. No use,
distribution or reproduction is permitted which does not comply with these terms.
Frontiers in Physiology | www.frontiersin.org 8October 2021 | Volume 12 | Article 761481