The Lille-based teams under Professors François Pattou (Lille University, Lille University Hospital, INSERM and the Institut Pasteur in Lille) and Philippe Preux (Lille University and INRIA) have developed a digital medical device which can predict the expected weight loss of an individual patient in the 5 years following their bariatric surgery. Based on 7 variables as well as artificial intelligence, it was developed from a cohort of 1,500 patients operated on and monitored for more than 15 years at Lille University Hospital. The effectiveness of the model was then validated among more than 10,000 patients monitored in France (Montpellier, Lyon, Valenciennes and Boulogne) and other countries (the Netherlands, Finland, Sweden, Switzerland, Singapore, Mexico and Brazil), as part of the European IMI Sophia project. The application is already online and available to healthcare teams and patients. The publication of these results in the prestigious Lancet Digital Health journal highlights the excellence of this original interdisciplinary project, initiated 3 years ago.