Introduction

Nowadays, it seems as though most Americans are trying to lose weight, and for good reason: about 97 million Americans are overweight or obese.^[1] These patients have increased risk of all-cause mortality, as well as increased morbidity from hypertension, dyslipidemia, type 2 diabetes, coronary heart disease, stroke, gallbladder disease, osteoarthritis, sleep apnea, and other respiratory problems, as well as certain malignancies, such as cancers of the endometrium, prostate, and breast.^[1]

The National Heart, Lung, and Blood Institute and the National Institute of Diabetes and Digestive and Kidney Disease published guidelines for the treatment of overweight and obese adults.^[1] These recommendations are intended for patients with a body mass index (BMI) ≥ 30, or ≥ 27 with obesity-related risk factors or diseases present. The guidelines recommend initial lifestyle modifications, including a reduced-calorie diet of 500-1000 calories per day, increased physical activity, and behavioral therapy. If these changes fail to produce a result in 6 months, approved pharmacotherapy is recommended as an adjunct in high-risk patients.

Prescription medications approved by the US Food and Drug Administration (FDA) for weight loss include: sibutramine (Meridia, by Abbott Laboratories), which inhibits the reuptake of serotonin, norepinephrine, and dopamine; orlistat (Xenical, by Roche Laboratories Inc.), a reversible inhibitor of gastric and pancreatic lipase; and phentermine, an adrenergic medication.^[2] Less commonly prescribed drugs include diethylpropion, benzphetamine, and phendimetrazine. Off-label medications for weight loss include newer antidepressants (fluoxetine, sertraline, bupropion) and novel anticonvulsants (topiramate, zonisamide).^[2] Bariatric surgery is recommended in cases of extreme obesity.

For many patients, exercise and a reduced calorie diet in addition to regular visits with their health provider is not only hard work, but also may also be a source of embarrassment. For these individuals, readily available herbs and dietary supplements that promise weight loss without a prescription are an attractive option.

These products are aggressively marketed to the public, and manufacturers claim they will produce significant weight loss without unwanted side effects. Yet, many of the ingredients have never undergone rigorous scientific testing, and claims about their effectiveness are often misleading.

Historically, sympathomimetic amines have been used as over-the-counter diet aids, including phenylpropanolamine, Ma Huang (ephedra), and ephedrine. However, these products became notorious for causing dose-related increases in blood pressure, which may not be problematic in healthy patients, but can be hazardous in others. When the use of phenylpropanolamine (Acutrim, by Amerifit Brands) was correlated with hypertension and stroke, the FDA banned it from the market in November 2000. Likewise, Ma Huang and ephedrine-containing supplements have been removed from the US market.

With the disappearance of these products, supplement manufacturers have struggled to bring a weight loss aid to market that is both safe and effective. Whenever media attention is given to a particular ingredient or supplement with potential thermogenic or appetite suppressant properties, overweight patients often are willing to give these products a try, even in the absence of properly conducted clinical trials.

Unfortunately, many patients fail to disclose their use of nonprescription supplements to their healthcare providers. Even if they did, many clinicians lack the training or expertise to analyze these therapies. In fact, it is not uncommon to hear a pharmacist tell patients, "We don't really have much evidence that this supplement will promote weight loss; however, it probably will not harm you."

The purpose of this review is to provide healthcare professionals with accurate information concerning the safety and efficacy of popular weight loss supplements, so that they can counsel their patients accordingly.