Transcranial Direct Current Stimulation to Modulate Brain Reactivity to Food Cues: Study Protocol of a Randomized Controlled Trial with fMRI (NeuroStim-Obesity)
Authors: Malmir Nastaran , Ghobadi-Azbari Peyman , Vartanian Meghedi , Mahdavifar-Khayati Rasoul , derafsheh Sara , Nitsche Michael A. , Nosratabadi Masoud , Ekhtiari Hamed 
Published: August 2020

Background: Obesity is one of the most serious public health concerns worldwide. Considering the multifactorial nature and increasing prevalence of obesity, many techniques have been proposed for its treatment, ranging from behavioral interventions to surgeries, but they are often ineffective, invasive, and costly. Furthermore, relapse and weight regain are common. Non-invasive brain stimulation techniques hold promise for modulating food-related brain processes and functions in these patients, potentially through increasing top-down control in response to food cue that supports reduction in calorie intake. Previous ﬁndings revealed that transcranial direct current stimulation (tDCS) over dorsolateral prefrontal cortex (DLPFC), a target site related to executive functions that support cognitive control of food craving, modulates the reward–control balance towards facilitation of cognitive control and possibly suppression of reward-related mechanisms that drive food cue-induced craving. However, understanding the neurocognitive mechanisms of tDCS over DLPFC on the brain networks of food craving remains largely unknown. Thus, an experimental clinical trial investigating the modulatory effects of tDCS over food cue-reactivity seems promising. Method: The NeuroStim-Obesity trial is a prospective, randomized, sham-controlled, double-blind single session tDCS trial targeting food craving in those with obesity. Once randomized, a total of 64 subjects (age range 18–61 years) with obesity (Body Mass Index (BMI) between 25-35 kg/m2) complete one session in which they receive either active or sham tDCS over the DLPFC. Active tDCS consisted of 2 mA of current applied continuously for 20 minutes with the anode placed over F4 and the cathode over F3 according to the 10–20 EEG system. The primary outcome is change in neural response to the food cue-reactivity task in the ventral striatum after a single session bilateral tDCS compared to sham stimulation. Secondary outcomes include changes in food craving evaluated by Food Craving Questionnaire-State (FCQ-S). We will also explore the predictive role of brain structural and functional networks assessed by structural, and functional magnetic resonance imaging (MRI) during both task performance and the resting-state that are acquired pre- and post-intervention to predict response to tDCS.Discussion: The results will provide novel insight into neuroscience for the efficacy of tDCS and will advance the field towards precision medicine for obesity. Exploratory results will examine the potential predictive biomarkers for tDCS response, and eventually to provide personalized intervention for treatment of obesity.Trial registration: This trial was retrospectively registered at Iranian Registry of Clinical Trials (IRCT) Identiﬁer: IRCT20121020011172N4 at June 4, 2020, https://www.irct.ir/trial/45482. This protocol was prepared in accordance with the SPIRIT guidelines (Chan et al., 2013a, 2013b).Funding: Funding for this study was provided by the “Cognitive Science and Technologies Council (CSTC) of Iran” to Masoud Nosratabadi at University of Social Welfare and Rehabilitation, Tehran, Iran.