Understanding safety concerns

Limited research also makes it difficult to judge the safety of a weight-loss supplement. And a product isn't necessarily safe simply because it's natural.

Ephedra, or ma huang, is an herbal stimulant that was once used in weight-loss products. In 2004, the FDA banned ephedra because of possible adverse effects, including mood changes, hypertension, irregular heart rate, stroke, seizures and heart attacks.

Bitter orange is a currently available herbal stimulant that is often called an "ephedra substitute" and is used in some weight-loss supplements. The active ingredient in bitter orange has chemical properties and actions that are similar to ephedra and may be associated with similar adverse effects. Because of limited research and the use of bitter orange in multi-ingredient supplements, the safety of the product isn't well-understood.

Researching before you buy

It's important to do your homework if you're thinking about trying over-the-counter weight-loss pills. General information about many dietary supplements is available at the website of the National Center for Complementary and Alternative Medicines.

The Natural Medicines Comprehensive Database summarizes research regarding dietary supplements and herbal products. Although the database is only available by subscription, you may be able to access it through a public library.

The following table shows common weight-loss pills and what the research shows about their effectiveness and safety.

Product Claim Effectiveness Side effects
SOURCES: JAMA, 2014; GLAXOSMITHKLINE CONSUMER HEALTHCARE, 2014; NATIONAL INSTITUTES OF HEALTH OFFICE OF DIETARY SUPPLEMENTS, 2014; NATURAL MEDICINES COMPREHENSIVE DATABASE, 2014; GASTROENTEROLOGY RESEARCH AND PRACTICE, 2011; JOURNAL OF THE INTERNATIONAL SOCIETY OF SPORTS NUTRITION, 2013.
Alli — nonprescription version of orlistat Decreases absorption of dietary fat Modest benefit, less effective than prescription-strength orlistat (Xenical) Loose stools, oily spotting, frequent or hard-to-control bowel movements; reports of rare but serious liver damage
Bitter orange (Citrus aurantium) Increases calories burned, suppresses appetite Possible modest benefit; very little data Increased heart rate and blood pressure; reports of anxiety, stroke, irregular heartbeat, heart attack
Chitosan (from exoskeleton of shellfish) Blocks absorption of dietary fat Probably ineffective; few well-designed studies Uncommon: upset stomach, nausea, gas, increased stool bulk, constipation
Chromium (essential mineral) Increases lean muscle mass, decreases appetite, increases calories burned Probably ineffective Uncommon: watery stools, headache, weakness, insomnia, nausea, vomiting, constipation, dizziness, hives
Conjugated linoleic acid (derived from dairy products and beef) Reduces body fat Possible modest benefit Upset stomach, nausea, constipation, loose stools; may decrease good cholesterol and increase bad cholesterol
Green coffee extract Reduces absorption of sugar (glucose), increases calorie and fat metabolism Possible modest benefit Excessive use: anxiety, agitation, insomnia, nausea, irregular heartbeat
Green tea extract Decreases fat absorption, increases calorie and fat metabolism Possible slight benefit Long-term use with high doses: insomnia, agitation, dizzinesss, nausea, vomiting, bloating, gas, diarrhea; reports of liver damage
Guar gum (derived from Indian cluster bean) Blocks absorption of dietary fat, increases feeling of fullness Probably ineffective Abdominal pain, gas, diarrhea
Hoodia (succulent plant) Decreases appetite Probably ineffective; insufficient data Headache, dizziness, nausea, vomiting; possible increase in heart rate and blood pressure
Raspberry ketone Increases fat metabolism Insufficient data Insufficient data

Including your doctor in your weight-loss plans

If you're considering weight-loss pills, be sure to talk with your doctor, especially if you have health problems, take prescription drugs, or are pregnant or breast-feeding. It's important to get advice on possible interactions with your current use of medicine, vitamins or minerals.

Your doctor can offer advice on losing weight, provide support, monitor your progress or refer you to a dietitian.

Dec. 19, 2014 See more In-depth