Background Trauma and obesity are both current global epidemics. A simple way to measure the body habitus of patients, to identify the overweight or obese is via the internationally recognized calculation of body mass index (BMI). The primary aim of this systematic review is to assess the mortality rate of those patients with a BMI > 30 kg/m² in relation to traumatic injury and secondly to assess the effect of those patients with BMI > 30 kg/m² upon the length of stay in hospital with regards to traumatic injury.

Method A systematic review of the literature was conducted via an internet search of databases and hand searching of references in identified publications from 1^st January 1990 to 17^th February 2018. Data was extracted from identified publications to include odds ratios of mortality and total length of stay in hospital (days) for patients with a BMI >30 kg/m² from included studies when compared to patients with a BMI <24.9 kg/m².

Results A total of 23 studies met the inclusion criteria. 32, 378 patients were admitted to hospital with a BMI >30 kg/m² and recorded injury severity score (ISS). Data collated identified BMI >30 kg/m² OR 1.66 (95% CI 0.75 – 4.2) vs BMI <24.9 kg/m² OR 0.93 (95% CI 0.82–1.5) to suffer mortality. ISS, BMI >30 kg/m²–19.93 vs 22.3 respectively. Furthermore, those categorised as BMI >30 kg/m² have 3.78 additional days in the hospital compared to those defined as normal weight.

Conclusion This systematic review presents a strong relationship of increased mortality and complications in trauma patients with BMI >30 kg/m². Complications are suggestive of those who have a BMI >30 kg/m² are more likely to suffer detrimental effects following trauma predominantly due to pre-existing unknown co-morbidities. Although, the direct relationship between obesity, trauma and mortality is not fully understood at present and requires more research.