A new study shows that obese teens who dieted, exercised, and took the fat-blocking pill Xenical lost more weight in a year than those who worked out, cut calories, and took a placebo pill.

However, that does not make Xenical a "magic bullet" against teen obesity. The teens were asked to make real changes in their habits besides popping pills. The pill's impact after a year isn't known; neither is its impact on overweight (but not obese) teens.

Gastrointestinal side effects were more common with Xenical, but no serious problems arose, say Jean-Pierre Chanione, MD, PhD, and colleagues. Their year-long study, published in The Journal of the American Medical Association, was funded by Xenical's maker, Hoffmann-La Roche.

Weighty Problem

Chanione's study starts by laying out the cold, hard numbers on teen obesity. The researchers say obesity is increasing among adolescents worldwide, growing by 15 percent to 23 percent in some ethnic minorities in the U.S.

Extra pounds aren't only burdening U.S. teens. The prevalence of overweight adolescents has grown by 8 percent to 21 percent in Northern Europe and 17 percent to 23 percent in Southern Europe, writes Chanione.

Chanione works at the endocrinology and diabetes unit of British Columbia Children's Hospital in Vancouver. He reports having received honoraria from Hoffmann-La Roche for speaker's presentations, says the journal.

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Beating the Odds

Losing extra weight is tough for many people, but adolescents are a "notoriously difficult to treat population," write the researchers. They point out that the "vast majority (83 percent)" of obese 10- to-15-year-olds become obese adults.

Of course, that fate is not written in stone. People can change course at any time. So while it's never too late to make positive changes, the sooner that happens, the better.

Obesity has long been linked to a host of health problems, including greater risk of heart disease, stroke, and cancer.

Xenical Drops Pounds

Chanione's study included 593 obese youths aged 12-16. They were seen at 32 U.S. and Canadian research centers. All of the teens had a body mass index (BMI) -- an indicator of body fat -- at or above the 95th percentile for their age.

Participants either took 120 milligrams of Xenical or a placebo three times per day for a year. The pills were identical, except the placebo lacked Xenical's active ingredient. The participants did not know which pill they were taking.

Xenical doesn't affect appetite. Instead, it helps promote weight loss by blocking about 30 percent of fat from getting absorbed into the bloodstream.

Guidelines for diet and exercise were issued, but the study doesn't say how many teens stuck to those plans.

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About a Third Dropped Out

About one-third of teens in each group dropped out during the study.

Reasons for dropping out were similar in both groups, say the researchers. The dropout rate of 35 percent to 36 percent is "well within what is usually seen in obesity trials, particularly those of more than one-year duration," write the researchers.

Study's Results

For the first 12 weeks, both groups lowered their BMI. By the year's end, the BMI had dropped 0.55 for the Xenical group, while it edged up by 0.31 with the placebo.

Some placebo takers lost substantial amounts of weight. Nearly 16 percent of them cut their BMI by 5 percent or more, and 4.5 percent cut their BMI by 10 percent or more.

However, the Xenical group beat them in both of those categories. More than a quarter of the Xenical group cut their BMI by 5 percent or more, and 13 percent had at least a 10 percent drop in BMI.

The Xenical group also trimmed their waistline, cut body fat, and lowered blood pressure more than the placebo group.

In conjunction with a reduced-calorie diet, exercise, and behavioral modification, Xenical significantly decreased BMI, waist size, and body fat compared with placebo, write the researchers.

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Side Effects

"No major safety issues were raised" in the Xenical group, says the study. Gastrointestinal problems were the most common side effects. Those were seen more with Xenical and included abdominal pain, nausea, and fatty or oily stools.

That's no surprise; those are known side effects of the drug and are due to the decreased absorption of fats.

Xenical can also reduce the absorption of some vitamins. Everyone in the study was taking a daily multivitamin.

Long-Term Impact?

The effects of long-term Xenical use by teens aren't known, write Chanione and colleagues. The drug's effectiveness and tolerability for more than one year of treatment has only been confirmed in adults, they write, calling for longer, bigger teen studies on the topic.

It also remains to be seen if obese teens would prefer a drug that curbs their appetite, writes Alain Joffe, MD, MPH, of Johns Hopkins University, in an editorial accompanying the study. Other questions include whether teens would regain pounds after stopping Xenical and what types of diet and exercise work best and appeal most to teens, writes Joffe.

Until those and other issues are clear, Xenical use for teens "should be limited to settings that offer comprehensive assessment and management of obese adolescents," writes Joffe. "There is no justification for using it as a standard treatment."

By Miranda Hitti, reviewed by Michael W. Smith, MD

SOURCES: Chanione, J. The Journal of the American Medical Association, June 15, 2005; vol 293: pp 2873-2883. WebMD Medical Reference from Healthwise: "Orlistat for Obesity." Joffe, A. The Journal of the American Medical Association, June 15, 2005; vol 293: pp 2932-2934. News release, JAMA/Archives.