Obesity, defined as BMI>30kg/M², is a growing problem in the US and worldwide. Multiple studies linked obesity to increased morbidity and mortality. Extremely obese patients present unique challenges to the inpatient physician.

It is reasonable to assume that obese patients do worse in the Intensive Care Unit as well. Yet, the clinical evidence on this issue is quite contradictory. Some studies showed a higher risk of death, while others revealed no difference in mortality or even showed a protective effect of obesity on ICU mortality. So, do chubby people do better in the ICU?

This would contradict common sense. It has been shown that obesity adversely affects metabolic, immune and microcirculatory functions leading to a higher incidence of hypertension, diabetes, dyslipidemia and infection.

Researchers from France (obesity study in France, really?) suggested that it is not the BMI, but the fat distribution that affects ICU morbidity and mortality. Specifically, it is abdominal obesity or belly fat that increases the risk of dying. It is not the weight but the shape that is important.

The study was published in the May issue of the Critical Care Medicine Journal. This elegantly conducted study showed that patients with predominantly abdominal obesity had a higher rate of death in the ICU independent of other predictors of mortality. BMI>30kg/m², by itself, did not affect mortality. I guess, some chubbiness could, actually, be protective in critical illness.

The researchers from France also found that the patient with predominantly abdominal obesity required renal replacement therapy (dialysis) and developed abdominal compartment syndrome more often than the control group. The higher risk of abdominal compartment syndrome is not a surprise – the sheer pressure of the fat on the abdomen can cause abdominal hypertension. I am still trying to wrap my mind around the fact that there was a higher incidence of renal failure.

In conclusion, not all fat is bad fat. Some chubbiness could, actually, be good for ICU patients. It’s the belly fat that could kill you or, at least, land you on a dialysis machine.