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  • Letter to the Editor
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Response to the Letter by Kawada

International Journal of Obesity volume 36, pages 1482–1483 (2012)Cite this article

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We appreciate the interest in our publication. Potential ethnic difference in adiponectin levels is certainly of great clinical interest and has been addressed in many recent studies in addition to the study quoted by Kawada. First of all, ethnic difference was not found in all studies. Second and perhaps more relevant to the comment is the fact that few studies separately analyzed the healthy subjects, an emphasis of our analysis. Meta-analysis depends on the availability of primary studies that can be used to test the hypothesis.1, 2 As described in the Introduction section, understanding the condition of healthy subjects is important in dissecting out factors that truly cause the obesity-related pathological changes and this is true in determining ethnic differences. Until more research effort is given to separately examine adiponectin of healthy subjects from different ethnic groups, it is not possible to conclude on the presence of an ethnic difference among healthy subjects. It is known that not all obese individuals develop metabolic abnormalities and normal weight individuals can also have abnormalities that are more frequently found in the obese population.3 The reason is not entirely clear and the evidence-based speculation on plasma free fatty acid level that we provided in our publication that Kawada commented on may be applicable here too.

Overall, epidemiological studies are to describe population behavior and can only statistically predict individual outcome. Two major factors that reduce the validity of meta-analysis are publication bias and selection bias.2, 4, 5 Publication bias is hard to verify in our case because of the limited number of trials that fit our criteria.6 It is known that negative findings such as trials that found no association between body mass index and adiponectin levels would have a harder time to be published.7 To avoid selection bias, we used Pubmed, a free database, for publication search and set up hypothesis-driven data exclusion criteria as described in the Method section. It is possible that limited publications and data existed outside the coverage of Pubmed but we included leptin analysis to confirm the quality of data used.

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  1. Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, NY, USA. E-mail: smkuo@buffalo.edu,

    S-M Kuo

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  1. S-M Kuo
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Kuo, SM. Response to the Letter by Kawada. Int J Obes 36, 1482–1483 (2012). https://doi.org/10.1038/ijo.2011.229

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