Duodenal-jejunal bypass liners (DJBLs) are a novel therapy with potential treating a range of metabolic diseases. This review discusses the weight loss and glycaemic improvements observed following the use of the DJBL.We summarize the evidence for the clinical application of DJBL to date. Within this, we outline the evidence available on the mechanisms of the observed effects.Based on the most recent trials, we cannot fully mimic the clinical or physiological effects of bariatric surgery with this device, but we are getting closer.