Dear DOCTOR Owen:

I recently saw an announcement of the release of Xenical® (Orlistat), a new fat-blocking agent, for weight loss. How does it work? Is it safe? Are there any side effects? It sounds too good to be true.

Fat Eater

Dear “Eater”:

Xenical® is an interesting newcomer to the medical scene, in more ways than one. It blocks the absorption of fat by binding irreversibly to lipase, an enzyme made by the pancreas and secreted into the intestine when fat is eaten. Lipase attaches to fat and breaks it into smaller molecules that can pass across the intestinal wall; then into the bloodstream; and eventually onto the hips, thighs, belly, and along the lining of the arteries! When the lipase is no longer available because the Xenical® binds it, the fat molecule remains too large to be absorbed, and passes into the colon where it become “waste,” part of the bowel movement.

Assuming that your diet is average American, you eat 30%–40% fat. Say, your daily maintenance calories (the amount of calories needed to run your body without weight gain or loss) amount to 1800, of which approximately 800 are fat. If you block 50% of this, you will not absorb 400 calories. Do this 7 days/week, and you will “save” 2800 calories. Do it for a month, and you will save 11,200 calories. Since 3500 calories make up 1 pound, you will save 3.2 pounds. Do this for a year and you will save 40 pounds!!!

As in all aspects of life, weight-management success comprises small changes that are carried out over long periods of time; and they add up. This is no different than saving your money for retirement, by budgeting a small savings every month. If you also make small changes in other foods—such as soft drinks, juices, and other items high in sugar—you will see even more striking weight changes.

The exciting fact that Xenical® is not absorbed, does not accumulate in the intestines, and has no other interaction with other substances or food, makes the compound, theoretically, riskless. Not many drugs can legitimately have such a statement made about their about safety profiles. In fact, the harmful substance—fat—does not cause side effects such as atherosclerosis (heart attack and stroke), hypertension, diabetes, and extra weight on the spine and joints. This drug is truly valuable, since these diseases are by far the most common, disabling, and expensive diseases on the planet. In early studies, over 40% of diabetic patients using Xenical® were able to stop their diabetic medications. Similar results are being seen on cholesterol levels and hypertension (high blood pressure) in patients who use Xenical®.

Now, the bad news. When fat is not absorbed, it acts much like mineral oil, resulting in diarrhea! The more fat in the colon, the looser the stool, which may have a terrible odor and cause soiling. Nevertheless, fewer than 2% of patients in studies to date have discontinued this drug because of bowel problems. Additionally, the pill must be taken with meals, so it must be carried around. It is also quite expensive and is, so far, not covered by insurance. Remember: The medical insurance industry considers obesity a character flaw! In spite of this, I firmly believe that Xenical® will be used as first-line therapy for elevated cholesterol, diabetes, and high blood pressure within several years after studies prove its benefit, even without “diet” instruction.

I warn my patients not to suffer from disinhibition—that is, eat more fat because they know that it won’t be absorbed if they take Xenical®. I can vouch, firsthand, that this occurs. I have been more tempted to eat fat while using this drug—which I am testing on my elevated cholesterol—instead of my cholesterol medication. Fat really does taste delicious. What a shame!