Are diet pills safe?

Q: Is there a diet pill available that is safe to use and really works?

A: I wish we had a pill that could help people lose weight easily. None of the medicines on the market are worth using, if you ask me.

Drugs for weight loss that are sold over-the-counter, such as dietary supplements and appetite suppressants don't have a strong effect on weight loss. And using these drugs can cause side effects.

Prescription weight loss drugs have drawbacks, too. They include orlistat (sold as Xenical and Alli), sibutramine (sold as Meridia) and phentermine (sold as Adipex and Ionamin). In some European countries, you can buy rimonabant (sold as Acomplia). It is not sold in the United States.

In November 2007, the British Medical Journal (BMJ) looked at the benefits and of prescription drugs for weight loss. The article summarized the weight loss results and side effects for orlistat, sibutramine and rimonabant.

The findings in this study closely matched a report on rimonabant that came from the U.S. Food and Drug Administration (FDA) in August 2007. It also is similar to FDA testimony about sibutramine at a Senate hearing in 2004.

How do these weight loss drugs "size up?" They are not very impressive. According to the BMJ study, after using the drugs for 1 to 4 years, people lost:

6 pounds on average with orlistat

9 pounds on average with sibutramine

10 pounds on average with rimonabant

Previous studies have found an average weight loss of 2 to 13 pounds with phentermine.

Most patients would need to spend more than $1,000 a year on the drugs in order to see these results. Cost is one reason that a lot of users don't stick with these medicines. A Canadian study showed that fewer than 10% of people who use sibutramine or orlistat stay with it for at least a year. Fewer than 2% of people stay with it for two years.

Another problem with weight loss medicines is their side effects:

Orlistat causes oily stool, grease spots on underwear, and uncomfortable urges to have a bowel movement in up to one-third of people who take it. It also may decrease the absorption of vitamins from your diet.

Sibutramine raises blood pressure and pulse rate. In up to 1 out of 5 patients, it can cause insomnia, nausea, dry mouth or constipation.

Rimonabant was associated with symptoms such as depression and anxiety in up to 1 out of 4 users. At usual doses:

9% of patients developed depression
5% needed to start medicine for depression
9% had to start an anxiety medicine or sleeping pill

The suicide rate doubled

Phentermine can cause a rapid heartbeat, high blood pressure, restlessness, anxiety, or diarrhea
Phentermine formerly was used along with the drug fenfluramine. This combination was known as Fen-Phen. In some people, it led to heart valve damage or abnormal artery pressures in the lungs. Fenfluramine is off the market. But similar problems might occur if phentermine interacts with drugs that are like fenfluramine. This includes antidepressants such as Prozac. These drugs can't be safely combined with phentermine.

Surely, there must be a better way to lose weight.

As old fashioned as it sounds, modest daily calorie intake and regular exercise are still the cornerstones of weight control. Weight loss drugs certainly can be a part of treatment for a person who is severely overweight. However, they are not good enough to substitute for other strategies. I don't recommend them for most people who need to lose weight.