The aim of this article is to present and discuss the unconscious psychological issues involved in bariatric surgery, in the light of the notion of the “weaning complex”. After highlighting the risk of postoperative suicide, we present the psychic mechanisms of decompensation among the patients concerned. We then recall that hyperphagia leading to obesity is a prevalent form of addiction in consumer societies. We also explore the notion of the “weaning complex” which was developed by Lacan, and show that bariatric surgery is a type of paradoxical and abrupt weaning. Based on the clinical case of a patient suffering from post-operative psychic decompensation and who was previously obese and addicted to food, the article explains that post-operative decompensation results from a major difficulty of shifting the drive satisfaction of food addiction to another object. In conclusion, we argue that restoring a taste for speech to these patients in the context of a clinical encounter is a central issue in countering the exacerbation of the death drive associated with the operation.