Neuromodulation With Transcranial Direct Current Stimulation (tDCS) to Control Excess Weight

The purpose of this study is to examine the effects of noninvasive neuromodulation with transcranial direct current stimulation (tDCS) aimed at enhancing the excitability of the left prefrontal cortex in middle-aged women with excess body weight. This is a randomized, parallel, double-blind study with a duration of 4 weeks. Outcome measures will include changes in performance in a computerized task assessing executive functions, subjective measures of food craving and appetite and changes in body weight.

A total of 40 subjects with overweight or class I obesity will be enrolled and randomized into either Group 1) Active tDCS or Group 2) Sham (control) tDCS. The duration of the study will be 4 weeks. During the first two weeks participants will receive eight sessions of tDCS. At week 2 they will also start a hypocaloric diet. The stimulation sessions (duration: 20 minutes, intensity: 2 mA) will be applied once daily (5 days in a row) during the first week and 3 alternate days (Monday, Wednesday and Friday) during the second week. At week 2 and until the end of the study subjects will also start a hypocaloric diet. The study aims are: To examine whether anodal tDCS applied over the left prefrontal cortex can improve executive functions/inhibitory control and reduce subjective ratings of food craving and appetite. To study whether anodal tDCS applied over the left prefrontal cortex, in combination with a hypocaloric diet, can facilitate weight reduction and maintenance over time.

The study is double blind. Neither the participants or the investigator delivering the intervention and collecting the outcomes will be aware of the group allocation. This is achieved via sham tDCS procedure and blinding of tDCS parameters with code system.

Subjects will receive a total of eight tDCS sessions: 1st week five daily sessions (Monday to Friday), followed by 2nd week three sessions only (Monday, Wednesday, Friday). tDCS sessions will consist of 20 minutes stimulation at 2mA. Target: left dorsolateral prefrontal cortex (DLPFC). Montage: 5x5 sponge electrodes placed over EEG 10:20 system location F3 (anode) and right supraorbital area (cathode).

Subjects will receive a total of eight tDCS sessions: 1st week five daily sessions (Monday to Friday), followed by 2nd week three sessions only (Monday, Wednesday, Friday). tDCS sessions will be sham stimulation (30-second ramp up and down). Target: left dorsolateral prefrontal cortex (DLPFC). Montage: 5x5 sponge electrodes placed over EEG 10:20 system location F3 (anode) and right supraorbital area (cathode).

Transcranial Direct Current Stimulation (tDCS) is a noninvasive form of neuromodulation that uses constant, low-intensity direct current delivered via electrodes that are placed on the head.

Change, evaluated via visual analogue scale (VAS). Self-reported scores to the question "How hungry are you?" representing the current state of the participant will be assessed with a horizontal line, 100 mm in length, anchored by the word descriptors "Not at all" and "Extremely", following standard methods, based on Blundell et al 2009.

Change, evaluated via scores in the State Food Craving Questionnaire developed by Cepeda-Benito (Moreno et al 2008).

Inclusion Criteria: Body mass index (BMI) between 25 and 35 kg/m2 Exclusion Criteria: Endocrinology disorder, such as diabetes mellitus or thyroid disease Addiction Neurological, psychiatric or any other major medical condition Hormonal therapy Contraindications to receive tDCS (past history of seizures or epilepsy, metallic implants on the head, skin disease or lesions in the area to be stimulated).

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