Orlistat (Alli or Xenical) Significantly Reduces Obesity

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New research suggests that the over-the-counter drug orlistat can significantly improve weight loss when combined with a low-fat diet.


Approximately two-thirds of the population in the United States is overweight, while at least a third of all people are obese.  Excess weight has clearly been linked to serious illnesses, including high blood pressure (hypertension), diabetes, cardiovascular disease, lung disease, liver disease, gallstones, and arthritis, among other potentially life-threatening ailments.  As I note in my book, A Cancer Prevention Guide for the Human Race, the extremely high concentration of fat and calories in modern processed foods, when combined with the sedentary lifestyles that most of us lead, almost guarantees a high level of obesity in our population.

Orlistat, which is available in both prescription and non-prescription forms, blocks the activity of lipase, an enzyme within the GI tract that breaks down dietary fats so that they can be absorbed.  Previous clinical research studies have shown that the addition of orlistat to a low-fat diet can significantly reduce body fat, and, in turn, can reduce the risk of illnesses that are associated with obesity.  Now that orlistat is available without a prescription, there have been concerns that this medication may be less effective, as it can now be purchased and taken without first having to enroll in a structured weight loss program.

A newly published study, which appears in the European Journal of Clinical Nutrition, suggests that non-prescription doses of orlistat (trade names Alli and Xenical) may still be an effective addition to the standard weight loss strategies of a healthy low-fat diet and exercise.  In this study, 27 obese research volunteers took over-the-counter orlistat (60 milligrams three times a day, with meals) for three months.  At the beginning and end of this study, the 27 volunteers were subjected to specialized imaging tests, including MRI scans, to measure the amount of fat in their bodies.  Blood pressure, heart rate, and cholesterol levels were also assessed.

In this clinical study, the use of over-the-counter orlistat, in combination with a reduced calorie, low-fat diet, was associated with a significant 11 percent reduction in body fat after 3 months.  Moreover, cholesterol levels, blood pressure, and heart rate all decreased, as well, following three months of orlistat combined with a prudent diet.

The findings of this study suggest that even over-the-counter orlistat, in conjunction with healthy eating habits, can significantly reduce both body fat and at least some of the adverse health effects associated with obesity.

Now for the bad news… orlistat works by blocking the absorption of fat from the GI tract, which means that 25 to 30 percent of the fat consumed while taking orlistat will remain within the GI tract until it is eliminated in the feces.  Unfortunately, high levels of undigested fat in the stool can lead to some rather unsettling symptoms, including flatulence, greasy/oily stools, bloating, and in some patients, an urgent desire to have a bowel movement.  On the other hand, while these symptoms are very common during the first few months of orlistat use, they appear to improve over time, such that only about one-third of patients taking orlistat will still have these symptoms four years after starting the drug.  Moreover, in patients who conscientiously maintain a low-fat diet while taking orlistat, the incidence and severity of these GI tract side effects are even lower.  (Another potential complication of orlistat is the reduced absorption of the fat soluble vitamins A, D, E, and K, although vitamin supplements will prevent significant deficiencies of these vitamins.)

While orlistat is associated with significant potential side effects, and thus should not be taken by everyone, the results of this small study do strongly suggest that orlistat is an effective option for obese patients who are able to both tolerate the drug’s side effects and remain compliant with a low-fat diet.  As always, however, I strongly recommend that you check with your primary physician prior to starting any new diet or medication, including orlistat.


For a groundbreaking overview of cancer risks, and evidence-based strategies to reduce your risk of developing cancer, order your copy of my new book, “A Cancer Prevention Guide for the Human Race,” from AmazonBarnes & NobleBooks-A-Million,Vroman’s Bookstore, and other fine bookstores!

On Thanksgiving Day, 2010, A Cancer Prevention Guide for the Human Race was ranked #6 among all cancer-related books on the Amazon.com “Top 100 Bestseller’s List” for Kindle e-books! On Christmas Day, 2010, A Cancer Prevention Guide for the Human Race was the #1 book on the Amazon.comTop 100 New Book Releases in Cancer” list!

Disclaimer:  As always, my advice to readers is to seek the advice of your physician before making any significant changes in medications, diet, or level of physical activity

Dr. Wascher is an oncologic surgeon, professor of surgery, cancer researcher, oncology consultant, and a widely published author

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