This topic and the evaluation of the meta-analyses and cohort studies from Germany is an important task which the authors have set themselves. However, they have failed to include the most important and largest meta-analysis – with 900 000 participants from 28 March 2009 – in their study (1); they just mention it. Although the authors report many facts more or less correctly, particularly in relation to mortality, their selection of topics and their occasionally inappropriate interpretation of the data are striking.
The authors repeatedly state that the overall mortality is not raised in overweight. Neither the WHO nor professional societies consider that this weight class presents serious problems with respect to mortality. Although the assertion that “a BMI of 27 kg/m2 in middle ages is now associated with the lowest mortality” is supported in the presented study, this is in disagreement with the current scientific evidence, as has been established for decades: “[…] mortality was lowest at about 22·5–25 kg/m2” (1).
The systematic analysis only included studies in which the BMI was used as the measure of obesity. More recent studies record waist circumference or the “waist-to-hip ratio” (WHR) as well as the BMI. These show a clear increase in mortality with increased waist circumference, even at normal BMI (2, 3). The authors’ conclusion must therefore be qualified as follows: Overall mortality is not increased in overweight – as measured by the BMI.
It is incomprehensible why the authors only use meta-analyses to evaluate comorbidities, as there are numerous studies of high level of evidence on many diseases associated with obesity. The assertion that “other diseases could not be identified” is a gross disregard of the current state of knowledge. A comprehensive presentation of obesity-associated diseases would have shown how frequent and severe the secondary diseases of obesity can be. Suitable parameters for the overall evaluation of morbidity include inability to work, premature retirement and the direct and indirect costs. Many comorbidities of obesity do not influence mortality, even though they are important diseases and greatly impair the quality of life.
Footnotes
Conflict of interest statement
Prof. Wirth is the local manager of the Sibutramin Cardiovascular Morbidity/Mortality Outcome Study, supported by Abbott GmbH.
References
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