Risks and benefits

Indication and risks
Orlistat is a powerful medication meant for people who are overweight or obese. Both Alli and Xenical are specifically approved to be taken only while also adhering to a low-calorie diet and exercise program. The OTC version, Alli, contains half as much as orlistat as doctor-prescribed Xenical does.

Orlistat works by blocking enzymes in the gut that normally digest fat, thus preventing its absorption. (During our review of the latest information one of our medical consultants commented that "fat malabsorption," as the condition is known, is actually a disease.) But that lack of absorption can lead to a number of adverse effects.  In clinical trials of Xenical, during the first year of use, 27 percent of people experienced oily underwear staining, 24 percent had gas with involuntary discharge of stool, 22 percent experienced fecal urgency, 11 percent had an increased number of bowel movements, and 8 percent suffered fecal incontinence. Virtually everyone who takes orlistat experiences diarrhea, at least, occasionally.

Most people can reduce the frequency and severity of those unpleasant side effects by cutting the amount of fat in their diets to 30 percent or less. But even then they must make other nutritional adjustments, since orlistat also hinders the absorption of fat-soluble vitamins, notably beta-carotene (vitamin A), vitamin D, vitamin E, and vitamin K.

In addition, the prescription version (Xenical) includes warnings on its label about the possibility of pancreatitis (inflammation of the pancreas).

The benefits
Even when orlistat is combined with exercise and nutritional changes, it produces only a modest 5 percent to 10 percent decline in body weight. Three studies done before the approval of orlistat measured weight loss over a one-year period in obese patients with and without type 2 diabetes. They had a BMI (body mass index) over 28 and were on a reduced-calorie diet. At the beginning of the trials, the patients weighed an average of 220 pounds. Pooled data show that the average weight loss with orlistat was about 19 pounds vs. 12 pounds with a placebo. Other trials found similar evidence of limited effectiveness.
But the most important question is: Does the evidence show that orlistat reduces premature death and disability? The answer is no. Even the manufacturer notes this in Xenical's drug labeling. A systematic review of the evidence published in the British Medical Journal on orlistat and two other weight loss drugs also found there was no evidence that it reduces death or the risk of cardiovascular disease.

It's true: Americans are getting fatter. The percentage of obese people in the U.S. has doubled—from 15 percent to 32 percent—in the last two decades. To stave off those unwanted pounds, consumers spend billions of dollars a year on weight loss products. While it is clear that weight loss in general can improve health, according to Consumer Reports medical advisors, orlistat is not the answer.

The bottom line
The risks of orlistat vastly outweigh the benefits. The millions of Americans who legitimately need to lose weight are far better off avoiding orlistat and weight-loss gimmicks. They should focus instead on what has been shown to work, without the risks: engaging in regular exercise, eating fewer calories, and sticking with both.