If you're relying on a handful of diet pills to help you avoid a serious case of "turkey tummy" and "pumpkin pie thunder thighs" this Thanksgiving, you may want to come up with a Plan B.

As the Associated Press and MSNBC report, researchers in Canada and Brazil have determined that the popular weight-loss pills Xenical and Meridia (plus Acomplia, which isn't available in the United States) only offer minimal weight loss - and often carry side effects such as insomnia, digestive problems, and nausea. Patients in the study lost an average of just 11 pounds using these diet pills, but most remained overweight even after a period of one to four years.

Still, every cloud has a silver lining. The study, reported in the British Medical Journal, found that these diet pills do offer some health benefits - including a reduced risk of diabetes, and lowered cholesterol levels - that may make their use worthwhile.

Patients using Xenical lost an average of seven pounds, and also saw lowered cholesterol and blood pressure levels, as well as a lower risk of diabetes; about 30% of patients experienced side effects.

Meridia users lost an average of nine pounds, along with lower cholesterol levels. Up to 20% suffered insomnia, nausea, and raised blood pressure and heart rates.

Finally, Acomplia users lost an average of 11 pounds and saw improved blood pressure and cholesterol levels; about 6%, however, experienced a heightened risk of mood disorders while on the drug. The drug was rejected by the FDA because of the risk of psychiatric side effects.

Researchers say that while diet pills are unlikely to cause significant weight loss, and do pose some health risks, the small weight loss they do provide can improve some people's health.

"Drugs are not the magic cure and are not for everybody," said study co-author Dr. Raj Padwal from the University of Alberta in Canada. "But in specific patients, they have great benefits."