Most weight loss drugs are for short-term use, meaning a few weeks or months.
One type of weight loss medication is "appetite suppressants." Appetite suppressants promote weight loss by tricking the body into believing that it is not hungry or that it is full. They decrease appetite by increasing serotonin or catecholamine, two brain chemicals that affect mood and appetite.
These drugs come in the form of tablets or extended-release capsules (pills that release medication over a long period of time). Appetite suppressants can be obtained by a doctor's prescription or bought over the counter. One common prescription appetite suppressant is phentermine. The FDA has also approved the appetite suppressant Belviq for long-term use in treating obesity. Side effects include dizziness, headache and tiredness.
The drug Qsymia combines phentermine with the seizure/migraine drug topiramate. Topiramate causes weight loss in several ways, including increasing feelings of fullness, making foods taste less appealing, and increasing calorie burning. Qsymia is designed to be taken long-term. However, it cannot be taken by pregnant women and is only sold through certified pharmacies.
Another type of prescription weight loss drug is a fat absorption inhibitor. They work by preventing your body from breaking down and absorbing fat eaten with your meals. This unabsorbed fat is eliminated in bowel movements.
Orlistat is the only drug of this type in the U.S. Orlistat works by blocking about 30% of dietary fat from being absorbed. Orlistat is available by prescription as Xenical and over-the-counter as Alli.
Does Xenical Really Work?
Xenical is moderately effective, leading to a 5% to 10% weight loss when taken along with a low calorie/low-fat diet. Most of the weight loss happens in the first six months.
Over the short term, weight loss from prescription drugs may reduce a number of health risks in obese people. But studies are needed to determine the effects of these medications over the long term.
The Risks of Prescription Weight Loss Drugs
When considering long-term weight loss drugs for obesity, the following concerns and risks should be discussed with your doctor:
Addiction. All prescription weight loss drugs except orlistat are "controlled substances." This means that doctors are required to follow certain restrictions when prescribing them since they could be addictive.
Tolerance. Most people's weight tends to level off after six months while taking a weight loss medication. This leads to a concern that the person has developed a tolerance for the medication, but this is unclear.
Side effects. Most side effects of weight loss drugs are mild (although some can be unpleasant) and usually improve as your body adjusts to the medication. Rarely, serious and even fatal side effects have been reported.