The Effect of Hypocaloric Diet Associated With tDCS on Weight Loss and Metabolic Profile

In order to assess whether tDCS treatment associated with a reduced caloric diet can improve weight loss, overweight or obese subjects will be recruited by advertisement on the web page of Porto Alegre Clinical Hospital, local newspaper and television, or referred by a doctor or nutritionist, from external to HCPA services. After screening and selection, patients will undergo a clinical, laboratory and nutritional evaluation. There will be a standard assessment protocol that includes: a complete clinical evaluation and socioeconomic status, assessment of physical activity, questionnaires of quality of life, sleep, depression and anxiety and body composition assessment. In the laboratory evaluation the biochemistry exams include an oral glucose tolerance test (OGGT 75g), a meal tolerance test (MTT), serum glucose, Cholesterol, HDL-cholesterol, triglycerides, glycated hemoglobin and glycated albumin. The resting metabolic rate will be determine by indirect calorimetry. Besides, a 100-mm visual-analog scales will be used to measure a self-reported ratings of appetite, hunger, satiety and food craving. Patients will also be prescribed a low caloric diet and individual counseling from a dietician in order to reduce 3% of their initial weight over 4-week treatment. Moreover, they will do one tDCS session a day (active or sham stimulation as previous randomization) for 5 consecutive days, during these four weeks of treatment (20 sessions). Transcranial direct current stimulation (tDCS) is a non-invasive method of brain stimulation in which a small current is applied to the scalp. This technique uses a weak safety current of 2 milliampere (mA) for 20 minutes which may increase (anodal tDCS) or decrease (cathodal tDCS) cortical excitability. During all of tDCS sessions, a film with images of food that usually elicit craving will be presented and after the end of each session, visual analog scales will be applied to assess hunger, satiety and presence of food craving. Finally, attention and mood scales will be applied periodically in addition to a questionnaire of adverse effects and use of tDCS. At the end of the 4-week diet and tDCS, all patients will be submitted to the same clinical, laboratory, nutrition and feeding behavior exams applied at baseline. Finally, participants should come in 3 and 6 months after the end of the protocol for reassessment weight, body composition by bioelectrical impedance and answer questionnaires. An interim analysis will be performed when 12 patients will be included.