Transcutaneous auricular vagus nerve stimulation for food craving: study protocol for a phase II randomized, sham-controlled clinical trial

Background and objectives: Obesity is one of the most important diseases around the world and it is an increasing issue for public health. Food craving is a usually noticeable symptom that is described as a “strong desire or urge to eat”. The vagus nerve and its relations to the neurocircuitry of the reward system play essential roles in the regulation of food intake. Transcutaneous stimulation of the auricular branch of the vagus nerve (taVNS) was previously described for its neuromodulatory effects in neuropsychiatric disorder. This study aims to investigate the effects of transcutaneous auricular vagus nerve stimulation on food craving in patients with obesity. Design: A two-arm, triple-blinded, randomized, sham-controlled phase II trial. Methods: This will be conducted at The Center for Neuromodulation Studies, Federal University of São Paulo, Brazil. Fifty-four subjects with food craving will be assigned to either: 1) a 10-session treatment protocol of real taVNS, or 2) a 10-session treatment protocol of sham taVNS. Participants will be evaluated for outcome measures before and after intervention, with a follow-up visit of 30 days after the end of treatment. Outcome measures: The primary outcome measure will be changes in food craving evaluated by Food Craving Questionnaire-State and Trait. The secondary outcomes will be improvement of anthropometric measures (body mass index and hip/waist ratio), metabolic profile (blood pressure, cholesterol and triglycerides levels and fasting glucose), dietary habits (dietary diary and Food Craving Inventory) and depressive symptoms (Inventory for Depressive Symptoms), and quantitative electroencephalography and heart rate variability. Discussion: To the best of our knowledge, there are no studies on the effects of taVNS on alleviating craving symptoms. Given the epidemiological situation and economic and social burdens, the possibility of modulating the reward system neurocircuitry through the vagus nerve using an easy-to-operate, low-cost, safe and potential at-home use method represents a breakthrough in the treatment of obesity. Ethics and dissemination: The study will be approved by the ethics committee from the Federal University of São Paulo, Brazil. Patient recruitment will initiate in October 2017; analysis of primary outcome measures will be completed in October 2018 and the study will be finished in October 2019. Dissemination plans include presentations at scientific conferences and scientific publications. Trial registration: ClinicalTrials.gov identifier: NCT03217929; registered on July 11th, 2017.