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• Cholesterol and blood pressure slightly lower
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NEW YORK (CNN) -- Obese people who took the experimental diet drug orlistat for two years lost an average of seven pounds more than people who did not take the drug, according to a new study.

But some scientists are questioning the significance of the results.

Orlistat, also called Xenical, is being considered for approval by the U.S. Food and Drug Administration.

Hoffmann-La Roche Inc., maker of the drug, funded the study published in this week's Journal of the American Medical Association.

Study participants were divided into two groups; both dieted and exercised. One group took orlistat, and the other took a placebo.

At the end of two years, the group taking the placebo lost an average of 10 pounds while the group taking orlistat lost an average of 17 pounds. The average person in the study weighed about 220 pounds.

Testing results may be not be significant

"Thinking on averages, I'm not convinced that a seven-pound difference will translate into meaningful long-term changes in health status," said David Williamson, a researcher at the Centers for Disease Control and Prevention who reviewed the study for JAMA.

According to Dr. Steven Heymsfield, the study's lead researcher, seven pounds may actually be an overestimate of the average weight loss because more than half the participants left the study before it was over.

He said these people probably did not lose much weight, or else they would have stayed in the study.

Therefore, since there are no final numbers for this group, the study may present orlistat as more effective than it really is, said Heymsfield, deputy director of the Obesity Research Center at St. Luke's-Roosevelt Hospital in New York.

Cholesterol and blood pressure slightly lower

Williamson said the results of the study were unclear, adding, "the true effect of this drug I'm not sure if we can determine accurately from the study as it was designed and implemented."

Heymsfield said a seven-pound weight loss probably would not make much of a health difference for someone who weighs 220 pounds, but said the drug "had very significant benefits" because it decreased cholesterol levels, blood pressure and glucose levels.

However, the study states that these changes were very small. Study subjects taking orlistat had a one-point decrease in blood pressure, and their "bad" (LDL) cholesterol levels went down just two points more than the study subjects who took the placebo. Glucose levels remained the same in both groups.

Insulin levels went down 18 points when people took orlistat. Some doctors say lower insulin levels can help protect against heart disease, but it's a controversial issue, Williamson said.

Orlistat is thought to work by blocking absorption of one-third of the fat consumed. Some people experience gastrointestinal problems while taking the drug, such as stomach cramping and diarrhea.