In Canada, the only prescription medication that is available for weight loss is orlistat (Xenical®). This medication is used along with a reduced-calorie diet by people with a BMI of 30 or higher who have not responded to an appropriate weight-reducing diet alone, and by people with a BMI of 27 or higher who also have other risk factors (e.g., high blood pressure, type 2 diabetes, abnormal cholesterol or triglyceride levels, excess body fat). It is also used to maintain weight loss and reduce the risk of regaining weight for people who have lost weight.

Previous medications for weight loss, including diethylpropion (Tenuate®, Tenuate® Dospan) and sibutramine (Meridia®), are no longer available in Canada.

Orlistat prevents enzymes (called lipases) that break down fat from working. This keeps fat in the intestine, and it passes through the body without being absorbed. Orlistat reduces fat absorption by about 30%. Weight loss is attributed to the resultant reduced caloric intake.

Orlistat is approved for use in combination with antidiabetic medications (sulfonylureas, metformin, insulin). Orlistat may help to improve blood sugar control for overweight or obese people with type 2 diabetes whose blood sugar is inadequately controlled by diet, exercise, and antidiabetic medication. Orlistat has also been shown to reduce the risk for diabetes in obese people.

The most frequent side effects of orlistat are:

  • abdominal pain
  • oily spotting of underclothes
  • inability to hold or sudden urge to have a bowel movement
  • gas with leaky bowel movements
  • oily bowel movements
  • increased number of bowel movements

The risk for these side effects is higher if more than 30% of your daily calories are obtained from fat, or if any single meal has a very high fat content.

Do not use orlistat if you have problems absorbing nutrients from foods. It should also not be used if you have problems with bile flow in your liver.

Orlistat may decrease the absorption of vitamins A, D, E, K, and beta-carotene. You may be advised to take a multivitamin containing these particular vitamins on a daily basis, at a separate time from when you take orlistat. For more information about orlistat, see our drug information article.

Speak to your doctor, pharmacist, or dietitian about weight management plans and resources available in your area.