Obesity and infection, accompanying phenomenon or causal association?

Open ArchivePublished:November 02, 2017DOI:https://doi.org/10.1016/j.cmi.2017.10.024
      Dear Sir,
      We commend the excellent work by Dobner et al. [
      • Dobner J.
      • Kaser S.
      Body mass index and the risk of infection—from underweight to obesity.
      ] who elegantly summarize the clinical evidence of links between body mass index (BMI) and the risk of infection [
      • Dobner J.
      • Kaser S.
      Body mass index and the risk of infection—from underweight to obesity.
      ]. We would like to address several points:
      First, Dobner et al. reviewed their topic in the population of children, adolescents, adults and the elderly [
      • Dobner J.
      • Kaser S.
      Body mass index and the risk of infection—from underweight to obesity.
      ]. However, a special but common population—pregnant women—was omitted. Ovalle et al. [
      • Ovalle A.
      • Martinez M.A.
      • Fuentes A.
      • Marques X.
      • Vargas F.
      • Vergara P.
      • et al.
      Obesity, a risk factor for ascending bacterial infection during pregnancy.
      ] demonstrated that obese pregnant women had 2.5 to 4.5 times increased risk of infections compared with normal weight counterparts.
      Second, one claim in the review [
      • Dobner J.
      • Kaser S.
      Body mass index and the risk of infection—from underweight to obesity.
      ] was that mortality of critically ill patients was reduced in obesity, which was called the ‘obesity paradox’. Whereas, as some experts [
      • Schultz M.J.
      • Spronk P.E.
      Overweight in ICU patients: is the body mass index reliable?.
      ] pointed out, most severely sick patients frequently need more fluids for resuscitation, which could lead to a higher BMI and make them ‘obese’. In this situation, BMI is unreliable, whereas the body fat content should be more objective and reliable.
      Third, some infectious agents might induce weight gain, AD-36, a human adenovirus, is the first human adipogenic virus reported [
      • Genoni G.
      • Prodam F.
      • Marolda A.
      • Giglione E.
      • Demarchi I.
      • Bellone S.
      • et al.
      Obesity and infection: two sides of one coin.
      ].
      Fourth, in Table 2 [
      • Dobner J.
      • Kaser S.
      Body mass index and the risk of infection—from underweight to obesity.
      ], Dobner et al. listed some potential confounders (including underlying disease, co-morbidities, nutrition, physical activity, smoking and well-being) of the reported associations between underweight or obesity and infection risk. Yet, some therapeutic regimens applied should not be ignored. For example, insulin has the ability to counteract metabolic changes and modulate inflammatory pathways in the pathogenesis of sepsis [
      • Andersen S.K.
      • Gjedsted J.
      • Christiansen C.
      • Tonnesen E.
      The roles of insulin and hyperglycemia in sepsis pathogenesis.
      ], which can help to control the sepsis, especially in the population of diabetes. Glycaemic control and steroids can also act as potential confounders.

      Transparency declaration

      The authors declare that they have no competing interests.

      Funding

      YY was supported by a grant from Guangdong Provincial Department of Science and Technology (Grant No. 2015A020210093 ). The funding sources had no role in the preparation, drafting, review or approval of the manuscript, nor in the decision to submit the manuscript for publication.

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        Obesity, a risk factor for ascending bacterial infection during pregnancy.
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        Overweight in ICU patients: is the body mass index reliable?.
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