Hindawi Publishing Corporation
Experimental Diabetes Research
Volume 2012, Article ID 672658, 8 pages
Effectsof Glucagon-LikePeptide-1 ReceptorAgonists on
Body Weight:A Meta-Analysis
Matteo Monami,1IlariaDicembrini,2Niccol` o Marchionni,1
CarloM. Rotella,2andEdoardo Mannucci3
1Geriatric Cardiology, Careggi Teaching Hospital and University of Florence, 50141 Florence, Italy
2Obesity Agency, Careggi Teaching Hospital and University of Florence, 50141 Florence, Italy
3Diabetes Agency, Careggi Teaching Hospital and University of Florence, 50141 Florence, Italy
Correspondence should be addressed to Edoardo Mannucci, email@example.com
Received 22 January 2012; Accepted 19 March 2012
Academic Editor: Giovanni Di Pasquale
Copyright © 2012 Matteo Monami et al. This is an open access article distributed under the Creative Commons Attribution
License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly
Glucagon-Like Peptide-1 receptor agonists (GLP-1RAs), approved as glucose-lowering drugs for the treatment of type 2 diabetes,
have also been shown to reduce body weight. An extensive Medline, Cochrane database, and Embase search for “exenatide,”
to December 15, 2011, with a duration of at least 24 weeks, comparing GLP-1 receptor agonists with either placebo or active drugs.
Twenty two (7,859 patients) and 7 (2,416 patients) trials with available results on body weight at 6 and 12 months, respectively,
were included. When compared with placebo, GLP-1RAs determine a reduction of BMI at 6 months of −1.0 [−1.3; −0.6]kg/m2.
Considering the average BMI at baseline (32.4kg/m2) these data means a weight reduction of about 3% at 6 months. This result
could seem modest from a clinical standpoint; however, it could be affected by many factors contributing to an underestimation of
the effect of GLP-1RA on body weight, such as non adequate doses, inclusion criteria, efficacy of GLP-1RA on reducing glycosuria,
and association to non-pharmacological interventions not specifically aimed to weight reduction.
show a sufficient efficacy and safety for long-term treatment.
In particular, agents which stimulate energy expenditure
(e.g., thyroid hormones, sympathoadrenergic drugs, or
sibutramine) do not have an adequate cardiovascular safety,
whereas centrally acting anorexants either are ineffective in
the long term (e.g., serotonin reuptake inhibitors) or show
neuropsychiatric adverse effects (e.g., amphetamine deriva-
tives or cannabinoid receptor antagonists) . As a result,
orlistat, which inhibits lipid absorption, is the only available
drug for obesity in many countries. Even for drugs which do
not show relevant problems of long-term safety, such as orli-
stat, the unsatisfactory tolerability profile limits clinical use.
Glucagon-like peptide-1 (GLP-1) is a gastrointestinal
hormone, produced mainly in the postprandial phase, which
stimulates insulin secretion and inhibits glucagon release in
a dose-dependent fashion . Due to this properties, the
hormone reduces hyperglycemia without inducing hypo-
glycemia in patients with type 2 diabetes . The rapid inac-
few minutes after subcutaneous administration) prevents its
therapeutic use. Long-acting GLP-1 receptor agonists, which
a day or once a week, have been developed as glucose-
lowering drugs for the treatment of type 2 diabetes , but
they have also been shown to reduce body weight [5, 6]. The
effects of GLP-1 and its agonists on body weight appears to
be due to a reduction in food intake, mainly determined by a
direct central (hypothalamic) effect of the hormone . The
stimulation of GLP-1 receptor also retards gastric emptying;
mediated via the autonomous nervous system . One of
associated with vomiting), could contribute to the weight
2 Experimental Diabetes Research
reducing effect; however, weight loss has also been observed
when analyzing separately patients who do not report nausea
In fact, some drugs of this class (i.e., liraglutide and
long-acting exenatide) are currently under development for
the treatment of obesity [9–12]. A phase II, 20-week trial
enrolling patients without diabetes showed that liraglutide
has a higher efficacy than orlistat in promoting weight
loss . Another longer-term (52 weeks) trial with same
molecule, the results of which have not been published in
full but partly disclosed , confirms that liraglutide is
an interesting option for the treatment of obesity. Another
molecule of the same class, exenatide, has been reported
to induce a significant weight loss in a 24-week placebo-
controlled trial . Most of what is known on the effect
of GLP-1 receptor agonists on body weight comes from
clinical trials performed on patients with type 2 diabetes,
with glucose control as the principal endpoint. Currently
ongoing trials enrolling subjects with obesity and without
diabetes will provide, in due time, further information. In
the meanwhile, a systematic evaluation of data collected in
of what we can realistically expect from GLP-1 receptor
agonists as weight-reducing agents.
A recent meta-analysis has shown a weight loss of
approximately 3% at endpoint in available published trials,
with a duration ranging from 20 to 52 weeks . This
analysis does not provide information on the time-course of
weight loss with GLP-1 receptor agonists. Furthermore, no
controlled trials, with some of the comparators (i.e., insulin,
thiazolidinediones, and sulfonylureas) possibly inducing
weight gain. Aim of the present meta-analysis is to assess the
effects of GLP-1 receptor agonists on body weight at 6 and
12 months of treatment, separating placebo-controlled trials
from comparisons with active drugs. Furthermore, a meta-
regression analysis will be performed to explore predictors of
weight change during treatment.
The meta-analysis was reported following the PRISMA
2.1. Data Sources, Searches, and Extraction. An extensive
Medline, Cochrane database, and Embase search for all ar-
ticles in English using the keywords “exenatide”, “lirag-
lutide”, “albiglutide”, “semaglutide”, and “lixisenatide” was
performed collecting all randomized clinical trials on
humans up to December 15, 2011. Completed but still
unpublished trials were identified through a search of http://
www.clinicaltrials.gov/ website. FDA (http://www.fda.gov/)
and European Medicines Agency (EMA, http://www.ema
.europa.eu/) reviews of approved drugs, as well as published
infor-mation provided to FDA in response to queries during
the approval process, were also searched for retrieval of un-
able, on http://www.novonordisk-trials.com/ or http://www
.clinicaltrials.org/. For unpublished and published trials
which were not exhaustively disclosed, an attempt was made
(through e-mail) to contact principal investigators in order
to retrieve missing data. For all published trials, results
reported in papers were used as the primary source of infor-
mation, when available.
The identification of relevant abstracts, the selection of
studies based on the criteria described previously, and the
subsequent data extraction were performed independently
by two of the authors (E. Mannucci, M. Monami), and
conflicts these resolved by the third investigator (N. Mas-
2.2. Study Selection. A meta-analysis was performed includ-
ing all randomized clinical trials, with a duration of at least
24 weeks, comparing full therapeutic doses Glucagon-like
Peptide-1 (GLP-1) receptor agonists (i.e., at least 1.8mg/day
liraglutide, 20μg/day for exenatide b.i.d., 2mg/day for
exenatide once weekly) and with placebo or other active
drugs. Trials with a shorter duration were excluded, due to
the fact that they could not yield relevant information on
body weight reduction. No review protocol was published
elsewhere. Trials without any information on body mass
index (BMI) at 6 or 12 months were also excluded.
2.3. Quality Assessment. The quality of trials was assessed
using some of the parameters proposed by Jadad et al. .
whereas some items were used only for descriptive purposes.
2.4. Data Synthesis and Analysis. The principal outcome was
compared with other hypoglycemic agents or placebo, on
BMI at 6 months and 12 months (when available). Between-
group differences in endpoint BMI were assessed as a
measure of treatment effect, without considering differ-
ences from baseline. Secondary outcomes included glycated
hemoglobin (HbA1c) at 6 and 12 months. Separate analyses
were performed for trials with different GLP-1 receptor
agonists and with different comparators, whenever possible.
Furthermore, separate analyses were performed for trials
with different principal endpoints. Metaregression analysis
was performed on placebo-controlled trials, in order to
identify possible predictors of weight loss.
Heterogeneity was calculated using the I2statistics.
Weighted mean differences were calculated for BMI and
HbA1c at 6 and 12 months, and a random effects model was
used for the meta-analysis. Publication/disclosure bias was
estimated separately for placebo-controlled trials and studies
versus active comparators, using Kendall’s tau without
continuity correction, and one-sided P, were calculated,
together with the fail-safe N, and Funnel plot analysis. All
those analyses were performed using Comprehensive Meta-
analysis Version 2, Biostat, (Englewood, NJ, USA).
The trial flow summary is reported in Figure 1. Trials with
available results on body mass index at 6 months were 21
Experimental Diabetes Research3
n = 127/157
Not randomized trials
n = 19/22
n = 1/0
No external comparison
n = 4/7
n = 55/77
n = 15/3
Already published on medline
n = 0/25
n = 12/23
Fulfilling all inclusion criteria
n = 21/0
N = 21
BMI at 6 months not available
Figure 1: Trial flow summary.
Difference in means
Funnel plot of standard error by difference in means
Figure 2: Funnel plot for bias/disclosure publication.
(19 of which in patients with diabetes), whereas those with
data at one year were 7 (6 of which on diabetes); the
characteristics of those studies are summarized in Table 1.
Funnel plot analysis on 6-month trials on diabetes (Figure 2)
as confirmed by Kendall’s tau (t = 0.14, P = 0.36) and fail-
safeN (numberofmissingstudiesthatwouldbringP > 0.05:
733). I2for BMI at 6 months was 83.6 (P < 0.001).
3.1. Results at 6 Months. Only two trials [15, 18] in
subjects with obesity not associated with diabetes reported
outcomes on body weight of exenatide at 6 months (with
a significant (P = 0.002) BMI reduction of 1.6 (0.6–2.5)
kg/m2in comparison with placebo). One further trial, which
enrolled patients with type 2 diabetes, had been designed
for the assessment of weight reduction with exenatide as the
principal outcome , with similar results.
In the 19 trials performed in patients with diabetes,
GLP-1 receptor agonists were associated with a significantly
lower BMI at 6 months in comparison with placebo and
with any active glucose-lowering agent, with the exception
of the only 2 available head-to-head comparisons with
thiazolidinediones. No differences in the weight-reducing
effects were observed between exenatide and liraglutide
(Figure 3(a)). A subgroup analysis of placebo-controlled
trials was performed on the basis of the minimum BMI
chosen as inclusion criterion; in trials excluding (N = 4)
or including (N = 5) nonoverweight (BMI < 25kg/m2),
the difference in 6-month BMI between active treatment
and control groups was −1.0 [−1.6; −0.4] and −0.8 [−1.3;
−0.3]kg/m2, respectively (both P < 0.001).
HbA1c, which was significantly reduced by GLP-1 receptor
agonists in comparison with placebo, DPP4 inhibitors,
and thiazolidinediones, whereas differences with respect to
sulfonylureas and insulin were not statistically significant
Metaregression analysis was performed on all placebo-
controlled trials, including those on nondiabetic individuals,
irrespective of the principal endpoint of the study. In the
11 available trials, mean baseline BMI, age, and duration of
diabetes (in the 9 trials on patients with diabetes) were not
significantly correlated with treatment effect on BMI.
3.2. Results at 12 Months. Results on BMI at 12 months were
available in 7 trials, 6 of which were performed in patients
with diabetes. The only one trial  enrolling subjects
without diabetes, which had weight loss as its principal
endpoint, liraglutide, induced a significant reduction of
in 1-year BMI; P = 0.04). The results of the other 6 trials, all
with active comparators, are summarized in Table 2. In these
studies, a further reduction of body weight was observed
after the first six months of treatment. Similar results were
obtained when the only trial which did not report 6-month
BMI  was excluded from the analysis (data not shown).
The few available trials designed with weight loss as the
principal endpoint and enrolling nondiabetic patients with
obesity have shown that GLP-1 receptor agonists have a
potential use as drugs for the treatment of overweight
[14, 15]. Similar results were obtained in a trial on over-
weight patients with polycystic ovary syndrome, in which
restoration of menstrual cycles was the principal endpoint
. The much wider evidence collected in subjects with
type 2 diabetes confirms this effect, as previously reported
[6, 18]. This action is consistent across trials, and it cannot
be attributed to selective reporting as shown by Funnel
4Experimental Diabetes Research
Duration of DM
BMI at 6-month
Marre et al. 
Nauck et al. 
Zinman et al. 
Russell-Jones et al. 
Nauck et al. #
Garber et al. 
Marre et al. #
Pratley et al. 
Russell-Jones et al. #
Diamant et al. 
Bergenstal et al. 
Bergenstal et al. #
Rosenstock et al. 
Elkind-Hirsch et al. 
Type 2 diabetes
Moretto et al. 
Buse et al. 
Buse et al. 
Kendall et al. 
DeFronzo et al. 
Derosa et al. 
Derosa et al. 
Gallwitz et al. 
Nauck et al. 
Heine et al. 
Bunck et al. 
#Studies with multiple comparators; NR: not reported; ID: interventional drug; C: comparator; DM: diabetes mellitus; wks: weeks.
Experimental Diabetes Research5
Table 2: Weighted mean differences in 6- and 12-month BMI between GLP-1 receptor agonists and different active comparators.
−1.2 [−1.5; −0.8]
−1.6 [−2.6; −0.8]
−1.4 [−2.4; −0.7]
−0.7 [−1.4; 0.0]
−1.9 [−3.0; −0.8]
−1.7 [−2.7; −0.7]
−2.3 [−4.2; −0.5]
−1.5 [−2.1; −0.8]
MD LL,95% CI UL,95% CI
MD LL,95% CI UL,95% CI
−1.6 −1.4 −1.2
−0.8 −0.6 −0.4 −0.20 0.2 0.4
Figure 3: Weighted mean differences in 6-month BMI (a) and HbA1c (b) between GLP-1 receptor agonists and different active comparators
or placebo, in trials performed in type 2 diabetic patients. MD: weighted mean differences; LL: lower limits; UL: upper limits.
6Experimental Diabetes Research
plot analysis and Kendall’s tau calculation. GLP-1 receptor
agonists have a beneficial effect on body weight not only in
comparisons with drugs that induce weight gain (such as
insulin or sulfonylureas) but also with respect to placebo.
thiazolidinediones: in this case, despite a mean difference
in 6-month BMI similar to that observed for other active
comparators, the statistical significance is not reached, due
to the small number of available trials.
In order to evaluate the weight reducing effect of
GLP-1 receptor agonists, the most interesting results are
those obtained in placebo-controlled trials, which allow to
discriminate the beneficial action of these drugs from the
adverse effects on body weight of other glucose-lowering
agents. In these studies, the mean weight loss at 6 months
is 1.0kg/m2; considering that the average BMI at baseline
is about 33.9kg/m2, this means that the actual ponderal
to be larger than that reported in a previous meta-analysis
; this result could be due to the exclusion of patients
treated with submaximal doses of GLP-1 receptor agonists.
This result could seem modest from a clinical standpoint;
however, several factors should be considered. In all trials on
patients with diabetes except one the principal endpoint was
the improvement in HbA1c, and not weight loss. This means
that patients were selected on the basis of unsatisfactory
glucose control, and not for their overweight; the minimum
BMI for inclusion was not specified in some studies, and
ranged from 25 to 45kg/m2in the others, meaning that,
in all trials, part of the patients enrolled were not actually
obese. Notably, those trials that excluded normal-weight
weight loss. Furthermore, patients with diabetes could have
greater difficulties in losing weight than similarly overweight
subjects with normal glucose tolerance. In those who had
elevated HbA1c at baseline, the reduction of glycosuria
determined by drug treatment could have been an obstacle
betes are not specifically aimed at weight reduction. All these
factors could have contributed to an underestimation of the
effect of GLP-1 receptor agonists on body weight. It should
also be recognized that weight loss in clinical trials could
be quite different from that obtained in real-life conditions.
The selection of patients with greater compliance and the
more accurate follow-up produces a greater weight loss from
baseline in randomized clinical trials. On the other hand, for
the same reasons, as long as the between-group differences
are assessed, as in the present study, the lifestyle/dietary
intervention associated with drug treatment in randomized
trials can partly mask the actual effect of the drug.
It should also be considered that treatment with GLP-1
receptor agonists could have some further beneficial effects
on other metabolic alterations of obese patients (e.g., insulin
resistance, risk of diabetes, blod pressure, etc.), beyond
weight loss. The assessment of those effects was not among
the aims of the present meta-analysis.
The effect of GLP-1 and its receptor agonists on food
intake and body weight is dose dependent . For this
reason, it is possible that doses needed for the treatment of
obesity are higher than those indicated for type 2 diabetes.
For example, liraglutide 3.0mg/day induces a greater weight
loss than 1.8mg/day, whereas no additional effect on blood
glucose is expected over 1.8mg/day . Obviously, at least
some of the adverse effects of these drugs (e.g., nausea
and vomiting) are also dose-dependent and they could be
amplified by the increase in daily doses. In the case that re-
commended doses for obesity exceed in a relevant manner
those for diabetes, the safety profile of GLP-1 receptor ago-
nists, which is satisfactory when they are used in the treat-
ment of type 2 diabetes, should be verified on a sufficiently
wide amount of data.
Some interesting information can be obtained from the
analysis of data collected in trials on type 2 diabetes with a 1-
year follow-up; in fact, the effect of GLP-1 receptor agonists
at 1 year seems to be larger than that observed, in the same
trials, after 6 months of treatment. The number of studies
is limited, and none of them includes a comparison with
placebo; in fact, a longer-term treatment without any active
drug would be unethical in patients with unsatisfactory
controlofdiabetes. Activecomparisonscanbemisleading, as
the comparators often induce weight gain (e.g., insulin, sul-
difference between GLP-1 receptor agonists and control
groups at 1 year could be partly due to weight gain induced
by comparators. Despite these limitations, the possibility
that the maximum effect of GLP-1 receptor agonists on
body weight is reached after 6 months should be considered
and taken into account in the design of future clinical
Conflict of Interests
M. Monami has received speaking fees from Astra Zeneca,
Bristol Myers Squibb, Eli-Lilly, Merck, Novo Nordisk, and
Takeda. I. Dicembrini has received speaking fees from Bayer,
Eli-Lilly, Novo Nordisk, and Takeda. C. M. Rotella has re-
ceived consultancy fees from Eli Lilly, research grants from
Eli Lilly, and speaking fees from Eli Lilly, Novo Nordisk, and
Sanofi-Aventis. E. Mannucci has received consultancy fees
from Merck and Novartis, speaking fees from Astra Zeneca,
Bristol Myers Squibb, Merck, and Novartis, and research
grants from Merck, Novartis, and Takeda. This work was
performed as part of the institutional activity of the authors,
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