Objective: To investigate the prevalence of overweight and obesity, and their impacts in patients admitted to a surgical
intensive care unit (SICU) in Thailand.
Material and Method: We conducted an analysis using the THAI-SICU database. All 4,579 patients who had weight and
height measured were classified into four groups using body mass index (BMI) based on the World Health Organization
criteria, which were 1) underweight (BMI <18.5 kg/m2), 2) normal BMI (BMI 18.5-24.9 kg/m2), 3) overweight (BMI 25-29.9 kg/m2), and 4) obese (BMI >30 kg/m2) groups. Primary outcome was prevalence of overweight and obesity. Secondary outcomes were 28-day survival, and SICU outcomes between four patient groups.
Results: There were 768 (16.8%) of underweight, 2,624 (57.3%) of normal BMI, 858 (18.7%) of overweight, and 329 (7.2%) of obese patients. Compared to other three patient groups, obese had the highest 28-day survival (log-rank, p<0.001), lowest incidence of systemic inflammatory response syndrome (SIRS) (underweight 41.1%, normal BMI 35.6%, overweight 34.5%, and obese 29.5%; p = 0.001), and lowest incidence of new infection (underweight 27.3%, normal BMI 23.3%, overweight 24.5%, and obese 20.4%; p = 0.047). After adjustment for related confounding factors, we found that every one unit increasing of BMI associated with lower risk of hospital mortality [odds ratio, OR, 0.97(95% confidence interval, CI, 0.94-0.99); p = 0.04], higher risk of acute respiratory distress syndrome (ARDS) [OR 1.06 (95% CI 1.03-1.08); p<0.001], and higher risk of intra-abdominal hypertension (IAH) [OR 1.06 (95% CI 1.03-1.09); p<0.001].
Conclusion: The prevalence of overweight and obesity in Thai critically ill surgical patients were 18.7% and 7.2%,
respectively. Compared to patients with lower BMI, patients with higher BMI had significantly lower mortality but greater
risk of ARDS and IAH.

Keywords: Obesity paradox, Obese, Mortality, ARDS, Intra-abdominal hypertension, ICU outcome