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Eating less and moving more are the basics of weight loss that lasts. For some people, prescription weight loss drugs may help.

You'll still need to focus on diet and exercise while taking these drugs, and they're not for everyone.

Doctors usually prescribe them only if your BMI is 30 or higher, or if it's at least 27 and you have a condition that may be related to your weight, like type 2 diabetes or high blood pressure.

Here's what you should know about the most common prescription weight loss drugs: orlistat, Belviq, Contrave, Saxenda, phentermine, and Qsymia.

Before you get a weight loss drug prescription, tell your doctor about your medical history. That includes any allergies or other conditions you have; medicines or supplements you take (even if they're herbal or natural); and whether you're pregnant, breastfeeding, or planning to get pregnant soon.

weight loss medicines

Orlistat

How it works: Blocks your body from absorbing about a third of the fat you eat.

When a doctor prescribes orlistat, it's called Xenical. If you get it without a prescription, it's called Alli, which has half of Xenical's dose.

Approved for long-term use? Yes.

Side effects include abdominal cramping, passing gas, leaking oily stool, having more bowel movements, and not being able to control bowel movements.

These side effects are generally mild and temporary. But they may get worse if you eat high-fat foods.

Rare cases of severe liver injury have been reported in people taking orlistat, but it's not certain that the drug caused those problems.

What else you should know: You should be on a low-fat diet (less than 30% of your daily calories from fat) before taking orlistat.

Also, take a multivitamin at least 2 hours before or after taking orlistat, because the drug temporarily makes it harder for your body to absorb vitamins A, D, E, and K.

Orlistat is the only drug of its kind that's approved in the U.S. All other prescription weight loss drugs curb your appetite, including the following.

Belviq

How it works: Curbs your appetite.

Approved for long-term use? Yes.

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