There are two basic types of weight loss drugs -- prescription drugs, which have been arou

Xenical (orlistat) is a fat blocker that prevents fat from being completely absorbed in the gastrointestinal tract. Prescription strength is 120 milligrams; over-the-counter Alli is the same drug at half strength, or 60 milligrams. Fat blockers reduce fat absorption and, as a result, some people are

Xenical or Alli is safe for almost anyone because the drug is not absorbed, says Kushner. "I frequently prescribed it to cardiovascular patients because it is so safe," he says. Patients must be willing to stick to a low-fat diet. These drugs have a built-in feedback system. "If you eat a high-fat diet, you will experience the side effects, so to avoid the unpleasant effects, you need to reduce the fat in your diet," says Aronne.