Obesity is on the advance in western industrialised countries and is therefore increasingly relevant also to intensive care medicine. In contrast to the common prejudice that obese patients probably have a higher ICU mortality than lean patients, convincing meta-analyses have revealed that this is not the case. Nevertheless, obese ICU patients are challenging. Especially mechanic ventilation has to be addressed: besides obesity-related anatomical problems that may complicate intubation, obstructive sleep apnoea, obesity hypoventilation syndrome and increased intra-abdominal pressure are of major relevance concerning ventilation, weaning and successful extubation. Also the risk of infections is increased in obese ICU patients, although this does not seem to increase the risk of sepsis. Nevertheless, the interplay of obesity and sepsis is a fascinating field in that adipous tissue is not just a passive reservoir of energy but an active endocrine and immunomodulating organ. However, the way of how adipokines interact with inflammation and coagulation in sepsis has yet to be clarified.