Weight loss pills bought over the Internet or at health food stores are considered dietary supplements and are loosely regulated (or, more often, not regulated at all). As such, there are very few double blind studies that actually prove they work. Anecdotal evidence often runs contrary to this. Many people who have used weight loss pills feel that they do work to some extent.

The risks involved
Despite the all-natural or herbal ingredients that many non-prescribed weight loss pills claim to be made of, some herbs are anything but safe. Many of these weight loss pills contain herb-based stimulants such as ephedra that can act very similarly to stimulants like amphetamines, causing your heart to race, or even worse, leading to liver failure or death. If you are planning to use weight loss pills, visit your health care practitioner and ask him or her to prescribe weight loss pills for you.

Prescription weight loss pills
Weight loss pills prescribed by a physician are considered medicines; they are regulated and safe for use. The three most common weight loss pills prescribed by a physician are Meridia, Xenical, and Phentermine. Meridia is a weight loss pill that is targeted towards severely obese individuals, while Meridia is contraindicated for people with heart conditions. Xenical is a weight loss pill that works by inhibiting the absorption of fat in the intestine, typically by 30 percent. Phentermine, an appetite suppressant that works best when combined with diet and exercise, is among the oldest prescribed weight loss pills on the market.