Orlistat (orlistat) is a weight-loss aid which interferes with fat absorption during digestion. It may also be used to help maintain lost weight. Treatment may last several weeks to several months or more, and is generally used in conjunction with improved dietary habits. 

Long-Term Weight Loss 

Orlistat is a lipase inhibitor, which means it inhibits digestion of fats; fats are eliminated as waste instead. This further enhances efforts to restrict fats in the diet, ultimately resulting in weight loss, though effects are modest without further attention to calories and carbohydrate intake. 

The medication comes in either 60 mg strength, which blocks around 25% of fat absorption, or 120 mg strength, which blocks about 30% of fat absorption. Multiple studies indicate there is no further benefit to be had by taking doses higher that 120 mg 3 times daily. 

To use, one tablet is taken with, or within 1 hour of, eating a meal which contains fat, up to 3 times daily. The medication provides no benefit if taken during a meal that does not contain fat, and may be skipped at such times. 

If a dose is accidentally skipped, it should be taken as soon as remembered up to 1 hour after eating. If it has been longer than 1 hour, skip it entirely and return to normal use with the next meal. There is no benefit in taking a double dose. 

While Taking Orlistat 

There are a few things to keep in mind to ensure maximum effectiveness and minimal side effects while taking this medication: 

• Orlistat, especially if used long-term, may interfere with the absorption of certain nutrients and vitamins as well as fat; namely A, D, E, K, and beta-carotene. A multivitamin supplement, taken at least 2 hours before or after orlistat, will help maintain a healthy balance.
• Similarly this medication may interfere with vitamin absorption in unborn or nursing babies, and as such should not be used by pregnant or nursing mothers, or by women actively trying to become pregnant. A contraceptive should be used for duration of treatment. 
  
• The most common side effect with this medication is oily spotting on clothes, resulting from increased gas and difficulty controlling bowels. This effect is considerably diminished if meals are kept to under 30% fat, and the fat consumed in a day is spread evenly among the three primary meals.
• Taking other medications or supplements along with this treatment is unlikely to cause serious side effects, but orlistat may inhibit absorption of some medications, interfering with effectiveness. Taking other medications at least 4 hours before or after orlistat will ensure they are absorbed properly.

As with most weight loss medications, effects are improved if improvements to diet are also made. Severely overweight individuals should seek advice from a doctor or nutritionist before making radical dietary changes, as rapid weight loss can be just as hazardous as being overweight. 

Common Side Effects 

Side effects from this medication are rarely serious, and only warrant medical attention if persistent or severe: 

• Gas
• Stomach upset
• Diarrhea
• Headache
• oily stools
• Oily spotting
• Frequent bowel movements
• Difficulty controlling bowels
• Light colored stools
• Changes in menstruation
• Fatigue

Patients with certain pre-existing conditions should use this treatment with caution and only under doctor's supervision: 

• Kidney or gallbladder issues
• Underactive thyroid issues
• Eating disorders
• Difficulty absorbing vitamins
• Malnourishment

Weight loss with this medication, or any rapid weight loss, may cause gallbladder stones. Symptoms include severe abdominal pain which may radiate to the back between the shoulder blades. This pain may last up to 6 hours. If this occurs, stop using orlistat and seek advice from a doctor.