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PharmD Student, College of Pharmacy, University of Tennessee, 847 Monroe Avenue, Room 205K, Memphis, Tennessee 38163, fax 901/448-4731
Associate Professor, College of Pharmacy, University of Tennessee
Published Online, March 6, 2007. www.theannals.com, DOI 10.1345/aph.1H234a
The authors calculated the study's sample size based on the primary endpoint, which was the change in weight during the study period. However, the study also had secondary objectives for which the authors performed statistical analysis and drew conclusions. Since the secondary objectives were not used to calculate the sample size, the sample size may not have been adequately powered to draw conclusions about the secondary objectives.
Additionally, the results were presented as mean ± SE instead of SD. The SD provides a true measure of variability about the study sample mean. Often SE is incorrectly used and gives the impression that the variability about the sample mean is less than it really is. SE does not represent the variability about the sample mean. Instead, SE correlates with how well the sample represents the population from which it was drawn.2
This study has additional limitations in that it does not address the efficacy of orlistat with normal fat intake. Restricted diet alone has been shown to produce favorable results.3 The hypocaloric diet used in the study would have produced weight loss on its own. By restricting the fat content of the diet, the authors have limited the efficacy of orlistat based on the mechanism of action of the drug. To adequately assess the efficacy of orlistat, the authors should not have restricted the amount of fat in the participants' diets.
Although this study shows that orlistat combined with diet management can help mildly to moderately overweight individuals lose weight, it is important to realize that the study has flaws both in design and statistical evaluation. External validity is limited, due to the low calorie diet, to which most people cannot adhere on a regular basis. With orlistat recently approved for over-the-counter sale, additional safety and efficacy data are warranted.
References
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