Body mass index as a biomarker for the evaluation of the Obesity Paradox among inpatients

Background: Overweight and obesity are, on the one hand, recognized as risk factors for many health related disorders, and, on the other, as favorable prognostic factors in various patients treated for several different conditions: what is called the obesity paradox. Until now, the existence of this phenomenon among a general population of consecutive inpatients has not been evaluated. We decided, therefore, to perform an evaluation. Patients and methods: Historical prospective analysis of the medical documentation of 23 603 hospitalizations during two consecutive years in one center was performed. The outcomes measured were as follows: length of stay, in-hospital all-cause mortality, and non-scheduled readmission in the 14-day, 30 day and one-year periods following discharge. Results: Overweight and obese patients had a lower or similar prevalence of the measured outcomes than malnourished patients and those of normal weight. Adjustment of the standard WHO BMI ranges for patients aged >= 65 y (normal weight BMI range 23-33 kg/m(2)) made these differences more apparent. In logistic regression, the ratio of fat to fat-free body mass was a stronger and unfavorable risk factor compared with BMI for the measured outcomes. Conclusions: The greatest risk of all-cause in-hospital death and readmission concerned malnourished inpatients. Compared to patients with a normal BMI range, overweight and obesity had a lower or similar (but not greater) risk of the outcomes measured. However, due to several BMI limitations, our observations should be interpreted as suggesting a BMI paradox, rather than an obesity paradox. (C) 2017 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved.