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2014 Guide to Diet Pills and Weight Loss Supplements

Are any products safe and effective?


Updated August 11, 2014

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

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The use of weight loss supplements is tempting. Who wouldn't want a little help to make the diet struggle easier? But there are hundreds of diet pills on the market. It can be confusing to sort through the claims and find a weight loss product that is safe and effective.

Prescription vs. Over-the-Counter Diet Pills

There are two categories of weight loss aids. Prescription medications are those that you would get with help from your doctor. Non-prescription, or over-the-counter (OTC) products, are the weight loss aids that you might find at the local vitamin store, drug store (without a prescription) or online.

As a general rule, the use of non-prescription weight loss products is discouraged by registered nutrition professionals. In a study published in the Journal of the American Academy of Nutrition and Dietetics researchers commented on their use. They said that "dietary supplements are not recommended as part of a weight-loss program due to concerns about efficacy and safety."

The Academy of Nutrition and Dietetics also addresses the use of prescription diet pills. In a position statement on weight management, they acknowledge that FDA-approved weight loss medications have shown some promise to help certain overweight and obese patients lose weight. They add, however, that medication should be part of a "comprehensive weight management program" that includes lifestyle changes and collaboration between health professionals.

The best resource for information regarding the use of any supplement or medication is your healthcare provider. Talk to your doctor about current research into the products that have grabbed your attention. Your doctor will also be able to discuss how taking a diet pill might interact with your other medications and will also be able to provide the best advice regarding the safety of new products.

Prescription Weight Loss Supplements

  • Phentermine. Phentermine is marketed under a long list of names, including Suprenza, Adipex-P, Kraftobese and Teramine. It is prescribed only for short periods and works by decreasing a dieter's appetite. According to the ADA, it is the most widely prescribed weight-loss supplement in the United States. However, the drug can be habit forming; side effects can include insomnia, constipation and dry mouth.
  • Xenical (orlistat). This prescription medication has been approved by the U.S. Food and Drug Administration (FDA) since 1999. Xenical is a lipase inhibitor, which means it works by blocking the absorption of fat. While that might seem to be the perfect weight-loss solution, there can be significant side effects, and the drug is meant to be combined with a low-fat, low-calorie diet.
  • Meridia (sibutramine). This appetite suppressant product was removed from the market in the United States in 2010. The FDA initially approved the product, but the manufacturer stopped producing it after clinical studies showed that users had an increased risk of heart attack and stroke. The National Institutes of Health (NIH) recommends that anyone still using Meridia contact their physician to discuss alternative treatments.
  • Qsymia.  This is one of two drugs that received FDA approval in 2012.  It is a combination of is a  two medications: phentermine and topiramate.  You can request a prescription of Qsymia from your physician if you have a BMI over 30 or a body mass index of 27 and higher along with a weight-related condition such as type 2 diabetes or high blood pressure. The medication needs to be taken along with lifestyle modifications for sustained weight loss.

  • Belviq (lorcaserin). This newly approved medication works by activating serotonin receptors that regulate hunger. By helping to control your appetite, drug makers hope that Belviq will help you feel full after you've eaten less food.  It is available with a prescription to patients with a BMI of 30 or a body mass index of 27 along with an obesity related condition.

Over the Counter Weight Loss Supplements

  • Alli (orlistat). This product has gained attention because it is a lower dose version of the drug orlistat, which is found in prescription Xenical. Alli is the OTC weight-loss product approved by the FDA. It works by blocking the body's absorption of fat. However, Alli is not a cure-all for obesity. For Alli to work properly, dieters still need to limit fat intake and make lifestyle changes. If you try to take the pill without making changes, side effects can be uncomfortable or even intolerable. Eating just one high fat meal may result in an inability to control bowel movements, loose or liquid stool, or oily discharge.
  • Garcinia cambogia.  This natural supplement is derived from a fruit that grows in warmer climates. It is widely available at health food stores and from online vendors, but many of the claims made by sellers have not been backed up consistently in published medical literature. One study published in Critical Reviews in Food Science and Nutrition said that there is still little evidence to support its effectiveness.
  • Conjugated linoleic acid (CLA)  This supplement has been studied extensively, but the results have been mixed.  Find out how much weight you can lose if you take CLA and check with your doctor before investing.  Some dieters experienced increased insulin resistance and lower levels of HDL cholesterol when taking the diet pills.
  • Ephedra, ephedra-free products and bitter orange. When ephedra was banned from the market in 2004, a number of similar stimulants took its place. Most advertise that they are ephedra-free and safe for dieters. They often contain bitter orange (citrus aurantium), synephrine or octopamine. Two of the most popular products, Xenadrine EFX and Advantra Z, were tested by researchers and still found to have unsafe effects on heart rate and blood pressure.
  • Chromium. Sometimes marketed as chromium picolinate, products that contain this substance often claim to help you burn extra calories and decrease your appetite. However, the NIH found that chromium has no significant benefits for weight loss. Chromium is generally considered to be safe, but it is likely to drain your wallet without any significant benefit to your waistline.
  • Green tea. Green tea can be consumed as a beverage or in pill form. It is often used to aid in weight loss or for improving mental alertness or lowering blood pressure. While green tea is safe when consumed in moderation, there is little evidence to support its use as a weight-loss supplement.
  • Hoodia. This herb is sold as a hunger suppressant for dieters. Hoodia is extracted from a flowering plant and can be consumed in tablet, pill or powder form. There is no scientific evidence to support the claims that hoodia is an effective appetite suppressant and its safety has not been verified.
  • Bee pollen. There is little evidence to support the use of bee pollen for weight loss.  In fact, the medical experts at ScienceBasedMedicine.org say that bee pollen is not safe or effective.  Once company was recently cited by the Centers for Disease Control for making false and misleading claims about the supplement's effects.

If the diet supplement that you are interested in is not listed above, visit the National Institutes of Health Dietary Supplement Fact Sheets website.  The NIH provides a comprehensive list of diet supplements along with current information about safety and effectiveness.


Chromium. Office of Dietary Supplements, National Institutes of Health. Accessed: November 28, 2011. http://ods.od.nih.gov/factsheets/chromium

Heidi Michels Blanck PhD, Mary K. Serdula MD, Cathleen Gillespie MS, Deborah A. Galuska PhD, Patricia A. Sharpe PhD, MPH, Joan M. Conway PhD, RD, Laura Kettel Khan PhD, Barbara E. Ainsworth PhD. "Use of Nonprescription Dietary Supplements for Weight Loss Is Common among Americans." Journal of the American Dietetic Association March 2007, Pages 441-447 .

EatRight.org Weight Management. American Dietetic Association. Accessed: December 15, 2011. http://www.eatright.org/About/Content.aspx?id=8382

Sharpe PA, Granner ML, Conway JM, Ainsworth BE, Dobre M. "Availability of weight-loss supplements: Results of an audit of retail outlets in a southeastern city." Journal of the American Dietetic Association. 2006 Dec;106(12):2045-51.

Haller CA, Benowitz NL, Jacob P 3rd. "Hemodynamic effects of ephedra-free weight-loss supplements in humans." The American Journal of Medicine 2005 Sep;118(9):998-1003.

Weight Control Information Network. "Choosing a Safe and Successful Weight Loss Program". U.S. Department of Health and Human Services, National Institutes of Health. Accessed: November 28, 2011. http://win.niddk.nih.gov/publications/choosing.htm

"Weighing the Evidence in Diet Ads". Federal Trade Commission. Accessed: November 28, 2011. Government PDF

"Dietary Supplements For Weight Loss. Limited Federal Oversight Has Focused More on Marketing than on Safety." Janet Heinrich
Director, Health Care-Public Health Issues. Accessed: November 25, 2011. Government PDF

Amelia Hollywood and Jane Ogden. " Taking Orlistat: Predicting Weight Loss over 6 Months." Journal of Obesity October 2010 .

Green Tea. National Institutes of Health, National Center for Complimentary and Alternative Medicine.. Accessed: November 28, 2011. http://nccam.nih.gov/health/greentea

Hoodia. National Institutes of Health, National Center for Complimentary and Alternative Medicine. Accessed: November 25, 2011. http://nccam.nih.gov/health/hoodia/

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