Obesity has increased rapidly in the United States, and
almost 65 percent of the general population is overweight
or obese. An even higher prevalence occurs among minority
subpopulations. It is the most common form of malnutrition
in the U.S. In the period of 2003-2006, 11.3 percent of
children and adolescents aged 2 to 19 years were at or above
the 97th percentile of the BMI for age growth charts, and
31.9 percent were at or above the 85th percentile.1
The health and cost implications of obesity are enormous.
Both overweight and obesity are implicated in the incidence
of a number of diseases, including pre-diabetes, type 2
diabetes, metabolic syndrome, cardiovascular disease,
hypertension, stroke, dyslipidemia, gout, osteoarthritis,
complications of pregnancy, polycystic ovarian syndrome
and some cancers. The association of morbidity with over-
weight and obesity is not clear but has been demonstrated
in several studies.2-4 Financial implications related to the
treatment of disease associated with overweight and obesity
is overwhelming. Public and private health care costs for
overweight and obesity accounts for 5.5 to 7 percent of
national health expenditures in the United States.5
Body weight is determined primarily by the ratio of energy
intake to energy output. If caloric consumption is higher
than caloric expenditure, weight gain ensues; conversely, if
either consumption decreases or expenditure increase,
weight loss will be seen.
A number of different nutritional approaches have been
employed in efforts to lose weight. These strategies fall into
three broad categories: (1) limiting the total caloric intake
(i.e., low-calorie diets), (2) altering the specific quality –
but not directly the quantity – of constituent dietary com-
ponents (e.g. low-carbohydrate diets, low-fat diets and the
like), and (3) use of dietary supplement additions to the
customary diet. While recognizing that rarely are any of
these strategies employed in isolation, the focus of this
article is the latter strategy.
The allure of a pill, whether pharmaceutical or nutriceutical,
which can allow one to shed pounds without making sacri-
fices at the dinner table, is irresistible. The quest for such an
agent drives the search for bariatric medications as well as
the burgeoning supplement industry. Over one-third of
adults report using a weight loss supplement at least once in
their life,6with nearly one in 10 having done so in the past
year.7These supplements may be purchased in pharmacies,
supermarkets, discount stores, gas stations and via mail
order, the Internet or direct-marketing sales.
The proposed mechanisms of supplements’ actions include
appetite suppression, metabolism boosting (e.g., “fat-burners”),
and inhibition of nutrient absorption (e.g., “fat- or carb-
blockers”). In spite of the plethora of formulations
available, there is little quantifiable evidence of safety or
efficacy for the top 10 most common ingredients.8
To date, there is no good evidence for any herbal appetite
suppressants. Garcinia cambogia (hydroxycitric acid) is
Obesity has reached epidemic proportions in this country. In an effort to address this major public health problem,
people have adopted a variety of strategies. These include medical and surgical interventions, both rational and fad
diets, exercise and assorted weight-loss dietary supplements. Recent U.S. Food & Drug Administration (FDA)
action involving some of these proprietary supplements raises questions of both their safety and efficacy. This
article reviews the evidence behind the components of many of these supplements and discusses the role of
nutrition in weight loss.
Weight-loss Supplements: What is the Evidence?
B y M a rk K. Hu n t i ng t o n, MD , P h D, FAA F P;
R o ge r A . S he w m a ke , P h D , L N
often marketed as an appetite suppressant but has not
demonstrated efficacy.9Studies of another agent similarly
marketed, chromium, show some benefit in the control of
diabetes, but this efficacy does not extend to weight loss.10
Phenylpropanolamine, a stimulant with appetite-suppressing
effects, was withdrawn from the market due to its
association with hemorrhagic stroke.
Eighty percent of supplements used contain naturally
occurring stimulants.7While there is evidence that some,
such as a combination of caffeine and ephedra,11 are
effective in helping with weight loss, the data suggests that
others (e.g., phenylephrine12) are not. Efficacy is only part
of the picture, however. “Natural” is not synonymous with
“safe,” and adverse reactions or toxicities are possible with
supplement use. Ephedra and other stimulants may be
arrhythmogenic.13Bitter orange (Citrus aurantium), a
supplement containing stimulant synephrin alkaloids,
shows promise for weight loss14 but has been associated with
ischemic colitis15 and angina.16 Usnic acid, which uncouples
oxidative phosphorylation, may be hepatotoxic,17as is
Garcinia cambogia, the subject of recent FDA action.18
These situations highlight the need to balance benefit with
risk, and the importance of having reliable data upon which
to base such risk management decisions.
Some of the absorption blocking supplements appear to
offer benefit for weight loss. For example, users of Phaseolus
vulgaris (bean) extract, which interferes with carbohydrate
absorption, lost more weight than those taking a placebo in
one small study.19 Phytosterols inhibit fat absorption and
lead to weight loss in animal studies, though no human
weight-loss data are currently available.20
Fiber has been hypothesized to aid in weight loss in two
ways: by increasing a sense of satiety with the fiber’s mass
displacing that of calorie-rich dietary components and by
decreasing absorption through increased gastrointestinal
motility. Empirically, fiber’s effect varies, with insoluble
fiber demonstrating efficacy in weight loss,21 while soluble
fiber22 and chitosan23 do not.
There has been the suggestion that increasing dietary calci-
um intake may aid in weight loss. This is based in part on
retrospective observational studies showing that increased
dairy consumption correlates with decreased weight.24
However, meta-analyses of randomized controlled trials fail
to find an effect of either calcium or dairy products on total
amount or rate of weight loss.25 Vitamin D supplementation
does not result in weight loss, either.26
Linoleic acid supplementation does not result in weight loss
but has been suggested to promote fat distribution to a
theoretically more healthy body habitus.27 However, other
studies suggest it does not do this and worsens endothelial
function, possibly increasing risk for cardiovascular morbidity.28
Assorted other supplements such as pyruvate, medium-
chain triglycerides, fiber and DHEA have been looked at in
small studies over short terms but have also shown inconsis-
tent results in regard to their value as weight-loss aids.
Partial meal replacement with supplements appears to work
in a number of studies,29-32 though it isn’t clear whether it is
the action of the supplements or simply the elimination of
the caloric content of the replaced meal that is responsible
for the effects seen.
In spite of the uncertain value of dietary supplements in the
promotion of weight loss, there is good news. An associa-
tion was seen between the use of supplements and both
lower initial body mass index and slower age-associated
weight gain.33 Additionally, those who use vitamin supple-
ments as a part of their weight-loss program are also more
likely to have an adequate intake of essential nutrients
when compared to those who do not take supplements.34
The bottom line on dietary weight-loss supplements is that,
while there is clearly potential, few have been adequately
studied and none can be definitively recommended at this
time.35There is a critical need for quality studies of the
potential role for supplements in weight loss.
Apart from weight-loss purposes, is dietary supplementation
wise? Many individuals do not meet recommended levels of
nutrient intake due to dietary and other lifestyle choices. As
a result, dietary supplementation may be advised. A good
example of this is vitamin D in northern climates, especially
among those with more deeply pigmented skin. There are
several recommendations for taking supplements that can
be made: Avoid mega-doses and choose supplements that
provide 100 percent of the daily value (DV)36 of all the
vitamins unless there is a diagnosed deficiency. The label
should state “United States Pharmacopeia (USP)” indicat-
ing the amount of nutrients listed is accurate and that it will
dissolve within 60 minutes. Many supplements now have
added herbs, enzymes or amino acids that may interfere
with medications such as anticoagulants and should be used
with close monitoring of therapeutic levels.
Overuse of multivitamin and mineral supplements is of
concern.37,38 There is a possibility that excessive vitamin A
can increase the risk of hip fractures,39 and excessive iron
intake could aggravate hemochromatosis.40 Other concerns
include vitamin B12 deficiency being masked by large
intakes of folate.41 Supplementation of single nutrients
sometimes can have adverse effects on the absorption and
utilization of other nutrients and medications. Beta
carotene, vitamin A and vitamin E may increase mortality.42-45
If calcium supplementation is needed, an additional
calcium supplement should be taken in addition to the low
amount that is in multivitamin and mineral supplements.
Supplementation as an Adjunct to Other Weight-loss Strategies
There are important nutritional considerations for patients
who pursue other strategies beyond mere dietary modifica-
tion for weight management. This includes those who
pursue pharmacological, surgical or exercise-based strategies.
A vitamin/mineral supplement that does not exceed 100
percent DV may be helpful if an individual is implementing
these weight-loss plans.
Surgical weight loss
Bariatric surgery is a well established technique to help
attain weight loss. Malnutrition is a risk associated with
surgery in general and especially with bariatric surgery.
Specific nutrient deficiencies are associated with both
restrictive and malabsorptive surgery. Preoperative and
postoperative nutritional education coupled with patient
compliance can alleviate many of the nutritional deficien-
cies and concerns of these surgeries.
The considerable decline in food consumption, changes in
appetite, and decreases in absorption lead to nutritional
deficiencies. Nutrients most likely to be consumed in lower
amounts and/or have lower absorption include vitamin
B12, folate, iron, thiamine (vitamin B1), calcium, vitamin
A, vitamin D, vitamin E and vitamin K. Macronutrient
concerns also exist for protein.46-48 Nutrition education can
help the patient select more nutrient-dense foods and
utilize appropriate supplements to avoid most deficiencies.
It has also has been shown to reduce food intolerances,
regurgitation and to increase the ability to tolerate a wider
range of solid foods. Post-surgery education in regard to diet
advancement schedules is also necessary.49
Pharmacological weight loss aids
The use of medications such as orlistat (Xenicalt™and
Allit™) inhibits gastric and pancreatic lipase production and
decrease fat absorption. Orlistat has been shown to help
minimize weight regain after weight loss and is well tolerated
overall.50 Anal leakage, diarrhea, fatty stools, soft stools,
increased bowel movements and flatulence may occur,
especially if higher-fat diets are consumed. Patients need to
be taught about fat intake to reduce the incidence of these
potential side effects. These side effects may result in failure
of the plan. Fat-soluble vitamin absorption may be
decreased and require the use of fat-soluble vitamin supple-
mentation.51 Weight loss medications such as Meridia™
(sibutramine), Redux™(dexfenfluramine) and various pre-
scription or over-the-counter stimulants that do not act by
altering absorption have no specific nutritional supplement
considerations beyond those for any calorie-restricted diet.
Summary and Recommendations
Several points mentioned in this article bear repeating.
First, in regard to dietary weight-loss supplements, there is a
lack of strong evidence of efficacy or safety. None can be
recommended specifically for weight loss at this time
(SOR=C).35 However, incorporating nutritional supplements
as a part of a calorie-restriction-based weight-loss plan and
for post-bariatric surgery patients results in better nutritional
status and is advisable (SOR=B).34, 49
Finally, it is important to understand that the proper nutri-
tional approach to weight loss emphasizes good overall
nutritional practices, with the goal being a healthful diet;
the specific amount of weight lost through its implementa-
tion is secondary.
Table 1. Additional Online Resources
1. Ogden CL, Carroll MD, Flegal KM. High body mass index for age among US children
and adolescents, 2003-2006. JAMA. May 28 2008;299(20):2401-2405.
2. Manson JE, Willett WC, Stampfer MJ, et al. Body weight and mortality among
women. N Engl J Med. Sep 14 1995;333(11):677-685.
3. Barbagallo CM, Cavera G, Sapienza M, et al. Prevalence of overweight and obesity
in a rural southern Italy population and relationships with total and cardiovascular
mortality: the Ventimiglia di Sicilia project. Int J Obes Relat Metab Disord.
4. Katzmarzyk PT, Craig CL, Bouchard C. Original article underweight, overweight and
obesity: relationships with mortality in the 13-year follow-up of the Canada Fitness
Survey. J Clin Epidemiol. Sep 2001;54(9):916-920.
5. Pi-Sunyer X, Kris-Etherton P. Improving health outcomes: future directions in the
field. J Am Diet Assoc. 2005;105( 5 Suppl 1):S14-S16.
6. Pillitteri JL, Shiffman S, Rohay JM, Harkins AM, Burton SL, Wadden TA. Use of
dietary supplements for weight loss in the United States: results of a national
survey. Obesity (Silver Spring). Apr 2008;16(4):790-796.
7. Blanck HM, Serdula MK, Gillespie C, et al. Use of nonprescription dietary
supplements for weight loss is common among Americans. J Am Diet Assoc.
Please note: Due to limited space, we are unable to list all references. You may
contact South Dakota Medicine at 605.336.1965 for a complete listing.
About the Authors:
Mark K. Huntington, MD, PhD, FAAFP, is Assistant Director, Sioux Falls Family Medicine
Residency Program, Center for Family Medicine, and Associate Professor, Department
of Family Medicine, Sanford School of Medicine at The University of South Dakota.
Roger A. Shewmake, PhD, LN, is Director of Nutrition, Sioux Falls Family Medicine
Residency Program, Center for Family Medicine; Co-chair, Society of Teachers of Family
Medicine Group on Nutrition; and Clinical Professor, Department of Family Medicine,
Sanford School of Medicine at The University of South Dakota.