The Obesity Paradox and Effects of Early Nutrition: Is There a Paradox, or Is There Not?*

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Excerpt

Obesity is a common problem in the United States. Roughly one in three adult Americans is classified as obese by the Centers for Disease Control (1). The effects of this widespread problem are pervasive throughout healthcare, with implications on care delivery, insurance cost, and ultimately patient quality of life. Despite the scope of this problem, it is unclear how being obese affects outcomes in the critically ill patient. Obese patients are commonly defined as those with a body mass index (BMI) greater than 30.0 kg/m2. These patients are at risk for a number of complications in the ICU (2). Many consider the obese patient as hypercoagulable and in a state of chronic inflammation due to their adiposity (3). This is supported by mechanistic research in animal models (4). Recent publications have argued this point and advocate that adipocytes may not only counteract the catabolic effects of sepsis and injury but may even immune-modulate some of the detrimental effects of the critically ill.
Much has been published regarding obesity and the obesity paradox in the critically ill patient (5, 6). Aspects such as reliability of BMI, nutrition in the critically ill obese patient, and mortality as it relates to the malnourished (obese and cachectic) patient have been studied, in addition to other related issues. Some of these studies are risk adjusted, most are retrospective, some are meta-analysis, and few may be generalizable to the reader’s home institution.
Rare is the clinician who would argue against the importance of early nutrition in any patient inhabiting the ICU regardless of BMI. Still, we are encumbered by the many facets our patients challenge us with including: ileus, repeat operations, and the nil per os orders rendered at midnight despite plans to return to the operating room at 3:00 PM the following day. This does not included difficulty with enteral access, dysphagia, nausea, vomiting, and many others. With the recommendations and position statements of various governing bodies such as the Society of Critical Care Medicine, contemporary practice dictates the clinician to consider/initiate enteral nutrition (EN) within 24–48 hours when possible. When this is not possible, parenteral nutrition should be considered at 7 days (7). This gives us the sense that nutrition is “critical” but not “urgent,” an interesting quandary.
Recently published data suggest that an obesity paradox exists (5). This proposes that rather than the associated mortality with increased BMI seen in the common population, critically ill patients have reduced mortality (8). Conversely, those with reduced BMI (18.5 kg/m2) suffer a higher mortality likely secondary to overall debility. The cachectic patient is often portrayed as the patient suffering from chronic obstructive pulmonary disease, cardiac disease, or cancer. These patients understandably carry a higher mortality regardless. It is difficult to accurately predict mortality in these patients.
In this issue of Critical Care Medicine, Harris et al (9) analyze over 1 million critically ill admissions from over 400 ICUs representing over 250 hospitals. Admissions were categorized by BMI and analyzed in terms of survival, length of stay, Acute Physiology and Chronic Health Evaluation IV score, gender, and nutritional status and several other common indices over a 7.5-year period, retrospectively. Stratifying mortality by BMI demonstrates some interesting conclusions that open the door for more research. It does reiterate that hospital mortality rates were lowest in the obese patient (BMI, 35.0–39.9 and > 50 kg/m2); however, when risk adjusted, this was not found to be significant. Additionally, when EN was added into the equation, there were no significant differences in nearly all categories of BMI stratification when compared to those with BMI of 25–29.9 kg/m2.

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