Review Article
Dietary supplements for body-weight reduction: a systematicreview1,2
ABSTRACT
tions such as type 2 diabetes, heart disease, cancer, and osteoar-
Background: Compliance with conventional weight-management
thritis of weight-bearing joints increases with body weight (2–5),
programs is notoriously poor, and a plethora of over-the-counter
and these conditions lead to substantial economic costs in the
slimming aids are sold with claims of effectiveness.
total health care budget (6). One factor responsible for over-
Objective: The objective of the study was to assess the evidence
weight and obesity is a continuous decrease in energy expendi-
from rigorous clinical trials, systematic reviews, and meta-analyses
ture from physical activity during recent decades (7, 8). Com-
on the effectiveness of dietary supplements in reducing body weight.
pliance with conventional weight-management programs is
Design: The study was a systematic review. Literature searches were
notoriously poor, which indicates a need for safe, effective, and
conducted on Medline, Embase, Amed, Cinahl, and the Cochrane
acceptable therapeutic options. It is therefore not surprising to
Library until March 2003. Hand searches of medical journals, the
see the marketing of a plethora of over-the-counter slimming aids
authors’ own files, and bibliographies of identified articles were
with claims of effectiveness (9, 10). The aim of this systematic
conducted. There were no restrictions regarding the language of
review is to critically assess the evidence from rigorous clinical
publication. The screening of studies, selection, validation, data
trials, systematic reviews, and meta-analyses on the effective-
extraction, and the assessment of methodologic quality were per-
ness of dietary supplements in reducing body weight.
formed independently by the 2 reviewers. To be included, trials wererequired to be randomized and double-blind. Systematic reviews andmeta-analyses of dietary supplements were included if they were
based on the results of randomized, double-blind trials. Results: Five systematic reviews and meta-analyses and 25 addi-
Systematic literature searches were conducted to identify all
tional trials were included and reviewed. Data on the following
randomized clinical trials (RCTs), systematic reviews, and meta-
dietary supplements were identified: chitosan, chromium picolinate,
analyses of dietary supplements for body weight reduction. Data
Ephedra sinica, Garcinia cambogia, glucomannan, guar gum,
sources were Medline, Embase, Amed, Cinahl, and the Cochrane
hydroxy-methylbutyrate, plantago psyllium, pyruvate, yerba maté,
Library. The search terms used were dietary supplements, food
and yohimbe. The reviewed studies provide some encouraging data
supplements, herbal products, phytotherapy, overweight, obe-
but no evidence beyond a reasonable doubt that any specific dietary
sity, weight loss, slimming, and derivatives of these. Each data-
supplement is effective for reducing body weight. The only excep-
base was searched from its inception until March 2003. Hand
tions are E. sinica– and ephedrine-containing supplements, which
searches of relevant medical journals and of the authors’ own
have been associated with an increased risk of adverse events.
files were conducted. The bibliographies of all articles located
Conclusions: The evidence for most dietary supplements as aids in
were searched for further studies. There were no restrictions
reducing body weight is not convincing. None of the reviewed di-
regarding the language of publication (11).
etary supplements can be recommended for over-the-counter
To be included, trials were required to state that they were
Am J Clin Nutr 2004;79:529 –36.
randomized and double-blind. Systematic reviews and meta-analyses of dietary supplements were included if based on the
KEY WORDS
Overweight, obesity, weight reduction, com-
results of randomized, double-blind trials. Studies assessing
plementary medicine, alternative medicine, herbal medicine, dietary
acute effects only were excluded. All studies were selected ac-
supplements, chitosan, guar, chromium, ephedra, psyllium, garcinia
cording to defined criteria, and data were validated and extractedin a systematic manner. Methodologic quality was evaluated byusing the system developed by Jadad et al (12). The screening and
INTRODUCTION
selection of studies, data extraction, validation, and the assessment
The number of persons whose body weight is greater than their
of methodologic quality were performed independently by the 2
ideal is increasing, particularly in developed countries. In theUnited States, for instance, more than half of the adult population
1 From Complementary Medicine, Peninsula Medical School, Universi-
must now be classified as overweight or obese. On the basis of a
ties of Exeter and Plymouth, Exeter, United Kingdom.
normal body mass index (BMI; in kg/m2) ranging from 18.5 to
Address reprint requests and correspondence to MH Pittler, Complemen-
tary Medicine, Peninsula Medical School, Universities of Exeter and Ply-
24.9, 31% of the US adult population is obese (BMI ͧ 30), and
mouth, 25 Victoria Park Road, Exeter EX2 4NT, United Kingdom. E-mail:
an additional 34% is overweight (BMI ͧ 25; 1). Excess body
weight is one of the most important risk factors for all-cause
morbidity and mortality. The likelihood of developing condi-
Accepted for publication September 24, 2003. Am J Clin Nutr 2004;79:529 –36. Printed in USA. 2004 American Society for Clinical Nutrition
reviewers. Disagreements in the evaluation of studies were largely
All 3 trials that reported on adverse events and an additional trial
due to reading errors and were resolved through discussion.
using niacin-bound chromium (Table 1) reported no adverseevents in patients receiving chromium. Ephedra sinica
Five systematic reviews and meta-analyses based on the re-
E. sinica, or ma-huang, is an evergreen shrub native to central
sults of double-blind RCTs and 25 additional double-blind RCTs
Asia (50). Ephedrine, the primary active constituent of the bo-
met all inclusion criteria. The identified evidence relates to
tanical E. sinica, has been studied alone and in combination with
ayurvedic herbal preparations, chitosan, chromium picolinate,
caffeine. A systematic review of 5 double-blind trials, including
Ephedra sinica, Garcinia cambogia, glucomannan, guar gum,
2 trials whose format as randomized or nonrandomized is not
hydroxy-methylbutyrate, plantago psyllium, pyruvate, yerba
clear, concluded that the combination of ephedrine and caffeine
maté, and yohimbe (Tables 1 and 2).
is effective for reducing body weight and appears to outweigh therisks (Table 2) (38). The most rigorous review to date (39) as-
Ayurvedic preparations
sessed human studies with ͧ 8 wk of follow-up and concluded
We identified one double-blind RCT assessing ayurvedic
that E. sinica and ephedrine promote a modest short-term weight
herbal preparations (13). Included patients whose body weight
loss of Ȃ0.9 kg/mo more than does placebo (Table 2). The in-
was ͧ 20% greater than their ideal according to the Life Insur-
take of those supplements, however, is associated with a 2.2- to
ance Corporation of India received daily either indistinguishable
3.6-fold increase in odds of psychiatric, autonomic, or gastroin-
placebo or ayurvedic preparations (Table 1) plus 750 mg
testinal symptoms and heart palpitations. Because of safety
Triphala/d. Patients in the treatment group experienced a reduc-
concerns, the FDA is now taking several regulatory actions
tion in body weight ranging between 7.9 and 8.2 kg, which
with regard to ephedra and ephedrine-containing supplements
differed significantly from the reduction seen with placebo. Chitosan Garcinia cambogia
Chitosan is a cationic polysaccharide, which is produced from
Hydroxycitric acid is obtained from extracts of G. cambogia
chitin, a substance derived from the exoskeleton of crustaceans.
and has been shown to inhibit citrate cleavage enzyme, suppress
It is promoted as a remedy to reduce fat absorption (41), and data
de novo fatty acid synthesis and food intake, and decrease body
from preclinical studies exist to support this notion (42– 44).
weight gain (20). We identified a double-blind RCT, which
However, data from our meta-analysis of 5 double-blind RCTs,
tested the effects of 3 g G. cambogia extract/d, which contained
which included patients who were described as either obese,
50% hydroxycitric acid, in patients with an average BMI of 32
overweight, or having 10 –25% excess body weight, indicated
(20). The results suggest the absence of a significantly greater
serious methodologic limitations of the clinical evidence (36).
weight loss in the treatment group than in the placebo group. Two
The meta-analysis concluded that the effectiveness of chitosan
further double-blind RCTs report effects in favor of treatment
for body-weight reduction is not established beyond a reasonable
with G. cambogia compared with placebo (Ramos et al, unpub-
doubt. We identified 5 further double-blind RCTs (Table 1) as-
lished observations; cited in 20, 21). This is supported by a trial
sessing overweight or obese patients that had been published
testing the effects of hydroxycitric acid (22). Other double-blind
since the meta-analysis. Overall, the evidence available in the
RCTs, however, that tested G. cambogia extract– or hydroxy-
literature indicates that there is considerable doubt that chitosan
citric acid– containing combination preparations with or without
is effective for reducing body weight in humans. Adverse events
dietary alterations (Kaats et al, unpublished observations; cited
most frequently included gastrointestinal symptoms such as con-
in 20, 23–25) report conflicting results. Overall, the evidence for
stipation and flatulence (Tables 1 and 2). G. cambogia is not compelling. Adverse events are reported inthe reviewed trials and are listed in Table 1. Chromium picolinate Glucomannan
Chromium, an essential trace mineral and cofactor to insulin,
enhances insulin activity and has been the subject of studies
Glucomannan is a component of konjac root, derived from
assessing its effects in carbohydrate, protein, and lipid metabo-
Amorphophallus konjac C. Koch. Its chemical structure is sim-
lism (45– 47). Reported effects include an increase in lean body
ilar to that of galactomannan from guar gum (see below) and
mass, a decrease in percentage body fat, and an increase in the
comprises a polysaccharide chain of glucose and mannose (53).
basal metabolic rate (19, 45, 48). Chromium picolinate is an
We identified one double-blind RCT including patients with
organic compound of trivalent chromium and picolinic acid, a
body weight ͧ20% over their ideal (26). The report suggests
naturally occurring derivative of tryptophan. Our meta-analysis
significantly greater weight loss in the treatment group than in the
included 10 double-blind RCTs (Table 2). The results suggest a
placebo group. There were no adverse events in the treatment
relatively small reduction of 1.1–1.2 kg (ie, 0.08 – 0.2 kg/wk)
group. Independent replication of this trial is warranted.
compared with placebo during an intervention period of 6 –14 wkin patients with an average BMI of 28 –33 (37). By comparison,
a diet with a provision of 3300 kJ/d achieves a mean weight loss
Whether guar gum, a dietary fiber derived from the Indian
of Ȃ1.5–2.5 kg/wk, and a more moderate energy restriction to
cluster bean (Cyamopsis tetragonolobus), is effective in lower-
5000 kJ/d results in a weight loss of 0.5– 0.6 kg/wk (49). There-
ing body weight was assessed in our meta-analysis (40). Twenty
fore, it seems that the observed effect with chromium picolinate
double-blind, placebo-controlled RCTs were included, and the
is, although statistically significant, not clinically meaningful.
data from 11 trials were statistically pooled. The results of the
DIETARY SUPPLEMENTS FOR BODY-WEIGHT REDUCTION
TABLE 1 Randomized, double-blind trials of dietary supplements for body-weight reduction1
flatulence, stoolbulkiness,bloating, nausea,heartburn
consume a 5000-kJ/ddiet; exercise wasencouraged
TABLE 1 (Continued)
mass decreaseand P ҃ 0.06for lean massincrease
1 NR, not reported; NA, not applicable. 2 Quantification of the likelihood that bias is inherent in a trial, based on the description of randomization, blinding, and withdrawals (12). 3 n randomly assigned/n analyzed. 4 Unpublished observations, cited in reference 20.
meta-analysis suggest that guar gum is not effective in reducing
spect to fat mass (27, 28), while at least a trend toward an increase
body weight. The agreement between the individual RCTs con-
in lean body mass was reported from all trials, including those in
firms the overall result of the meta-analysis. Adverse events
which it is unclear whether the patients and care providers were
reported in the reviewed trials predominately relate to the gas-
blinded. Thus, there are encouraging data that require further
independent replication. Only 2 of the 4 trials provided data onadverse events (54), and they reported no such events in patients
Hydroxy-methylbutyrate
treated with -hydroxy--methylbutyrate.
-Hydroxy--methylbutyrate is a metabolite of leucine that
has shown anticatabolic actions through inhibiting protein break-
Plantago psyllium
down (54). -Hydroxy--methylbutyrate is available as a dietarysupplement and is primarily used by bodybuilders as a supportive
Psyllium is a water-soluble fiber derived from the husks of ripe
measure to induce changes in body composition. The searches
seeds from Plantago ovata (50). We identified one double-blind
yielded 4 RCTs reported in 3 articles (54, 27, 28). Two double-
RCT, which included patients with type 2 diabetes and a mean
blind RCTs reported significant intergroup differences with re-
BMI of 29 (29). There were no significant changes in body
DIETARY SUPPLEMENTS FOR BODY-WEIGHT REDUCTION
TABLE 2 Systematic reviews and meta-analyses of dietary supplements for body-weight reduction1
to change theireating habitsand to exerciseregularly
hypertension (7),upper gastrointestinalsymptoms (88),headache (16),
1 RCTs, randomized controlled trials; NR, not reported; NA, not applicable. 2 n randomly assigned/n analyzed. 3 Not defined in original trials. 4 Data from double-blind, placebo-controlled trials are presented; it is unclear whether 2 of the 5 studies were randomized. 5 Data from all identified studies are presented. 6 Data from controlled trials are presented.
weight in either the treatment or placebo group. The authors
results of that study indicated that this combination preparation
report excellent tolerance of psyllium.
might potentially be effective in lowering body weight. Adverseevents were not reported. Pyruvate
Pyruvate is generated in the body via glycolysis, and supple-
mentation with pyruvate seems to enhance exercise performance
Yohimbe (Pausinystalia yohimbe) is a tall evergreen tree that
and improve measures of body composition (55, 56). Two
is native to Central Africa. Yohimbine, an ␣-2 receptor antago-
double-blind RCTs, which included patients with BMIs of ͧ25,
nist, is the main active constituent of the ground bark of P.
assessed the effects of pyruvate supplementation (30, 31). None
yohimbe. Most clinical studies relate to the effects of this isolated
of these studies reported significantly greater effects on weight
constituent of yohimbe bark. We identified 3 double-blind RCTs,
reduction than were seen with placebo. One (30) reported a
which included patients who were 15–20% over their ideal
significant body-weight reduction of 1.2 kg from baseline, while
body weight or had a BMI ranging between 28 and 48 (33–35).
both reported significant reductions in fat mass and percentage
These trials report conflicting results (Table 1). At present, there-
body fat from baseline. Considering the evidence available from
fore, it is unclear whether yohimbine is effective in reducing
rigorous clinical trials, the case of pyruvate as an aid to body-
body weight. Few adverse events were reported.
composition changes and weight loss is weak. No adverse eventsare reported in one trial, and the other did not report on adverseevents (Table 1). DISCUSSION
The data from published double-blind RCTs, systematic re-
Yerba maté
views, and meta-analyses are encouraging in some cases, but
Yerba maté (Ilex paraguariensis) is an evergreen tree that is
they provide little convincing evidence that any specific dietary
native to South America. In a combination preparation also con-
supplement is effective in reducing body weight. The only ex-
taining guarana (Paullinia cupana) and damiana (Turnera dif-
ceptions are E. sinica– and ephedrine-containing dietary supple-
fusa), it was tested in patients with a BMI of 26 –30 (32). I.
ments. These remedies, however, have been associated with an
paraguariensis and in particular P. cupana contain relatively
increased risk of adverse events. The relative paucity of compel-
large amounts of caffeine and have been shown by ultrasound
ling evidence to suggest the effectiveness of dietary supplements
scanning to prolong gastric emptying time (32). The descriptive
in weight loss confirms the findings of earlier reviews (57).
Lifestyle changes including dieting and regular physical ex-
of the evidence involved a degree of judgment in some cases,
ercise are the basis for successful long-term weight loss, and
which is another potential source of bias. However, we used a
limited evidence exists to support the effectiveness of pharma-
standard scale (12) to assess important criteria of methodologic
cotherapeutic options other than orlistat and sibutramine (58,
quality. This scale was also used in 4 of the 5 systematic reviews
59). Notoriously poor compliance with conventional weight-
and meta-analyses. The methodologic quality of the evidence
management programs and the popularity of complementary and
was combined in an informal process with the type of evidence
alternative medicine have created a ready market for nonpre-
(eg, RCT or meta-analysis) and the volume of evidence to pro-
scription weight-loss products. Data from a US survey of a ran-
duce an indication of weight. This process of appraising the
dom population sample of almost 15 000 adults, for instance,
clinical evidence was performed independedntly by the 2 review-
showed the common use of nonprescription weight-loss prod-
ucts, particularly among young obese women. It is interesting
In conclusion, according to our findings, the evidence for most
that 8% of women with no excess body weight were also reported
dietary supplements as aids in reducing body weight is not con-
vincing. None of the reviewed dietary supplements can be rec-
Although these preparations are popular, given the lack of
convincing data on effectiveness (60), even minor adverse events
MP was responsible for the conception and design of the study. MP and EE
shift the delicate risk-benefit balance against their use. There is
were responsible for the drafting of the manuscript, critical revision of the
no convincing evidence, for instance, that guar gum is more
manuscript for important intellectual content, and for final approval of the
effective than placebo (Table 2), whereas adverse events such as
manuscript. Neither of the authors had any conflicts of interest.
diarrhea, nausea, and flatulence were severe enough for 3% of thepatients in trials included in our meta-analysis to withdraw. These findings are corroborated by other reports in the literature
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Disciplines related to visual psychophysics and perception Speaker: Lothar Spillmann September 29, 2009 Visual psychophysics encompasses the beginning and the end of the visual processing chain. This is a great opportunity to learn more about the disciplines that deal with the intermediate stages. Let us start with the very beginning, dioptrics. Here, you want to understand how an i
GASTROINTESTINAL SPECIALISTS Aria Torresdale Medical Office Bldg. Barix Clinic 3998 Red Lion Rd S.242 280 Middletown Blvd Philadelphia, Pa 19114 Langhorne, Pa 19047 215-632-3500 215-702-7090 UPPER GASTROINTESTINAL ENDOSCOPY PREPARATION YOU ARE SCHEDULED FOR A GASTROSCOPY ON ____________________ DO NOT TAKE ANY FOOD OR LIQUID BY MOUTH AFTER MIDNIGHT THE NIGHT BEFORE YOUR PROCEDURE