Xenical is prescribed to be taken orally three times a day (roughly 360 milligrams of orlistat total), while Alli is taken orally with meals containing fat, up to three times a day (for a maximum of 180 milligrams daily).
Availability: Alli is available over-the-counter, while Xenical is available through prescription to "help considerably overweight people," according to the product Web site. After some initial success in selling the drug, GlaxoSmithKline reported a 50 percent drop-off in sales in its annual report for 2008, to roughly $150 million from $300 million in 2007.
Pros and Cons: Orlistat works by decreasing the amount of fat that the intestines will be able to absorb. In clinical trials for Alli, the drug, when accompanied by a change in diet, was shown to increase weight loss through dieting by an additional 40-60 percent.
For patients assuming the drug will burn off pounds, the labels explain otherwise.
While the drug does assist in adding to number of pounds a user can shed, it does require changes in diet and can have some undesirable effects on the digestive system, particularly when not used properly. "Gas with oily spotting," "loose stools" and "more frequent stools that may be hard to control" are among the listed side effects.
What is it? Bariatric surgery is a name used for a number of surgeries that can ultimately lead to weight loss.
"We typically call it metabolic surgery now," explained Dr. Lee Kaplan, director of the weight center at Massachusetts General Hospital, "because not only does it cause weight loss, but it improves diabetes and lipid disorders like cholesterol and other things."
Bariatric surgery is typically used in patients who are significantly overweight, often with an eye towards fixing problems that arise from obesity, such as type 2 diabetes and sleep apnea.
Availability: According to estimates from the American Society for Metabolic & Bariatric Surgery, about 220,000 Americans underwent the surgeries last year, up from 205,000 in 2007. In 2000, 36,700 procedures were performed.
Pros and Cons: Bariatric surgery is called for in someone who is significantly overweight and requires a number of lifestyle changes to ensure that the surgery helps a patient lose weight.
Generally patients would need to have a body mass index above 35 in order to be considered for the procedure. They also must be able to undergo surgery and participate in follow up.
What is it? While liposuction is often portrayed as an operation where large amounts of fat are sucked out of the body, it is not used for major weight loss -- only for toning certain areas by removing some fat. The most weight a patient will lose in liposuction is only 10 to 12 pounds.
Availability: Liposuction has been on the decline in recent years. According to the American Society of Plastic Surgeons, 245,138 liposuction operations were performed in 2008, a drop from 301,882 operations performed in 2007 and 354,015 performed in 2000.
Pros and Cons: Liposuction is a cosmetic procedure that might enable someone to tone their body as they would like, but will not lead to significant weight loss.
The weight loss interventions discussed previously are by no means the only ones around. ABC News OnCall+ has gathered experts from around the country to answer questions about these and other wellness concerns.