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Xenical (orlistat) is one of the most common, FDA-approved weight-loss drugs doctors prescribe to their patients. However, it is usually recommended only for people who are considered obese, based on their body mass index (BMI, a measure of fatness). A person who has a BMI of 30 or more, which is calculated based on one's height and weight, is considered obese. Xenical may also be prescribed to patients who are overweight (with a BMI of 27 and above) if they have a medical condition such as diabetes or high blood pressure, that may be worsened by being overweight.

Individuals who are overweight with a BMI of 25 or higher who want to use this drug can obtain a preparation with lower strength, which is available without prescription.

How it Works

Fat from foods is absorbed in the intestines and transported by the blood to the liver and later, to the rest of the body.

Orlistat prevents the intestines from absorbing some (about 1/3) of the fat we ingest from food.

The fat that is not absorbed passes through the intestines and into the stool. This results in taking in fewer calories, which leads to weight loss when taken regularly.

Xenical is taken three times a day within one hour of eating meals. People who do not eat a lot of fat in their meals do not need to take Xenical. Unlike other weight-loss drugs, orlistat does not reduce or suppress your appetite.

Side Effects of Xenical

Xenical is considered to be a safe drug. However, like other drugs, it also has side effects. Common side effects include the following:

  • Stomach cramps

  • Increased frequency of bowel movements

  • Inability to control bowel movements.

  • Intestinal gas with your bowel movements

  • Oily stool

  • Oily spotting on underwear

  • Nausea and vomiting

  • Symptoms of liver disease (yellowing of skin and eyes)

  • Symptoms of kidney disease (pain during urination, back pain)

Doctors also warn that Xenical can reduce absorption of vitamins A, D, E, and K, since these are fat soluble vitamins. One should therefore take multivitamin supplements when taking Xenical to offset this effect.

Does Xenical Work?

According to research, taking Xenical regularly, combined with a low-calorie meal results in greater weight loss compared to placebo. One study involving more than 3,000 obese patients also showed that over a four-year intervention period, taking orlistat combined with lifestyle changes can reduce the risk for developing type 2 diabetes, in addition to weight loss.

Some patients have reported a failure to lose weight, or having gained more weight after using orlistat for months. However, one study shows that the reason for weight loss failure in some patients is that they stopped taking the medication because of the side effects or fear of the side effects. A deeper look into the patients found that some of these patients continued to eat a high-fat diet, which resulted in having side effects such as frequent bowel movements and oily stool.

The researchers believe that physicians need to educate their patients that orlistat will work only if it is combined with eating a low-fat diet that includes less than 30% of their daily calories from fat.

Experts also advise that one should not rely on weight-loss pills alone to achieve healthy weight, but to combine medicine intake with a balanced low-calorie diet, regular exercise, and other healthy lifestyle changes.

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