Several weight-loss medicines are available. Ask your health care provider if any are right for you.
About 5 to 10 pounds can be lost by taking these medicines. But not everyone loses weight while taking them. Most people also regain the weight after they stop taking them, unless they have made lasting lifestyle changes, such as exercising and cutting unhealthy foods from their diets.
You may also see ads for herbal remedies and supplements that claim to help you lose weight. But many of these claims are not true. Some of these supplements can have serious side effects.
Note for women: Pregnant or nursing women should never take diet medicines. This includes prescription, herbal, and over-the-counter remedies. Over-the-counter refers to medicines, herbs, or supplements you can buy without a prescription.
ORLISTAT (XENICAL AND ALLI)
About 6 pounds can be lost when using this medicine. But not everyone loses weight while taking it. Many people regain most of the weight within 2 years after they stop using it.
The most unpleasant side effect of orlistat is oily diarrhea that may leak from the anus. Eating fewer fats can reduce this effect. Despite this side effect, most patients are able to tolerate this medicine.
Xenical is the brand of orlistat your health care provider can prescribe for you. You can also buy orlistat without a prescription under the name Alli. These pills are half the strength of Xenical. Orlistat costs about $100 or more a month. Consider whether the cost, side effects, and the small weight loss you can expect are worth it to you.
Your body may not absorb important vitamins, minerals, and other nutrients from food while you are using orlistat. You should take a daily multivitamin if you use orlistat.
PHENTERMINE, BENZPHETAMINE, AND PHENDIMETRAZINE
These medicines stimulate your brain. This means they will make you more alert. They also make you less interested in food.
Some of these stimulants are approved for treating obesity. The average weight loss while taking these medicines is about 5.8 pounds. But not everyone loses weight while taking them. Most people regain the weight after they stop taking the medicine, unless they have made lasting lifestyle changes.
These medicines are available only by prescription. They include:
Phentermine (Ionamin, Adipex-P, Fastin)
Phentermine combined with topiramate (Qsymia)
Phendimetrazine (Adipost, Bontril, Melfiat, Plegine, Prelu-2, and Statobex)
Phentermine is the most commonly prescribed of these medicines. It costs less than orlistat. But like orlistat, its effects do not last long. Some side effects of phentermine are:
Increase in blood pressure
Problems sleeping, nervousness, palpitations, dry mouth, and constipation
Depression, which many people who are obese struggle with already
Note: If you have diabetes that needs treatment with medicines, you may want to ask your doctor about diabetes medicines that cause weight-loss. These include:
Metformin (Glucophage, Glumetza, and Fortamet)
These medicines are not approved by the FDA to "treat weight-loss". So you should not take them if you do not have diabetes.
Screening for and Management of Obesity in Adults. Rockville, MD. US Preventive Services Task Force; June 2012: AHRQ publication 11-05159-EF-2.
David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Bethanne Black, and the A.D.A.M. Editorial team.