Effects of Home-Based Transcranial Direct Current Stimulation on Appetite

Acute change in appetite is assessed using the Appetite Visual Analog Scale (VAS) immediately before and after the first daily stimulation session on Days 7, 14, 21, and 28. The acute effect is defined as the change in Appetite VAS score from immediately before to immediately after stimulation. The Appetite Visual Analog Scale ranges from 0 to 10, with higher scores indicating greater appetite.

Chronic change in appetite is assessed using the bedtime Appetite Visual Analog Scale (BT-VAS), measured once daily before bedtime from Day 1 through Day 28. The chronic effect is evaluated based on the change in bedtime Appetite VAS scores over time during the 4-week intervention period. The Appetite Visual Analog Scale ranges from 0 to 10, with higher scores indicating greater appetite.

Change in body weight measured in kilograms (kg) from baseline to Week 4.

Change in body mass index (BMI), calculated as body weight in kilograms divided by height in meters squared (kg/m²), from baseline to Week 4.

Change in body fat percentage, measured as a percentage (%), from baseline to Week 4.

Change in waist circumference measured in centimeters (cm) from baseline to Week 4.

Change in skeletal muscle mass measured in kilograms (kg) using bioelectrical impedance analysis from baseline to Week 4.

The Dutch Eating Behavior Questionnaire (DEBQ) assesses restrained, emotional, and external eating behavior using 33 items rated on a 5-point scale. The restrained eating subscale consists of 10 items, yielding a total score ranging from 10 to 50; higher scores indicate greater dietary restraint and stronger conscious control of food intake. The emotional eating subscale consists of 13 items, yielding a total score ranging from 13 to 65; higher scores indicate a greater tendency to eat in response to emotional states. The external eating subscale consists of 10 items, yielding a total score ranging from 10 to 50; higher scores indicate a greater tendency to eat in response to external food-related cues. Changes in the three DEBQ subscale scores will be assessed from baseline to Week 4.

The Reward-Based Eating Drive Scale-13 (RED-13) assesses reward-based eating, including loss of control over eating, lack of satiety, and preoccupation with food. The 13 items are rated from 1 to 5 and summed to yield a total score ranging from 10 to 65. Higher scores indicate greater reward-based eating drive. Change in RED-13 total score will be assessed from baseline to Week 4.

The General Food Cravings Questionnaire-Trait (G-FCQ-T) assesses trait-like general food craving. It consists of 21 items rated from 1 to 6, yielding a total score ranging from 21 to 126. Higher scores indicate greater trait food craving. Change in G-FCQ-T total score will be assessed from baseline to Week 4.

The General Food Cravings Questionnaire-State (G-FCQ-S) assesses current or momentary food craving. It consists of 15 items rated on a 5-point scale from 1 to 5, yielding a total score ranging from 15 to 75. Higher scores indicate greater current food craving. G-FCQ-S scores will be assessed repeatedly on Days 7, 14, 21, and 28 during the 4-week intervention period.

The Behavioral Inhibition System (BIS) scale consists of 7 items rated on a 4-point scale from 1 to 4, yielding a total score ranging from 7 to 28. Higher scores indicate greater sensitivity to punishment and stronger behavioral inhibition. Change in the BIS score will be assessed from baseline to Week 4.

The Behavioral Activation System (BAS) scale consists of 13 items rated on a 4-point scale from 1 to 4 and comprises three subscales: Reward Responsiveness (5 items; score range, 5-20), Drive (4 items; score range, 4-16), and Fun Seeking (4 items; score range, 4-16). Higher scores indicate greater reward responsiveness, stronger goal-directed drive, and greater fun-seeking tendency, respectively. Changes in the BAS subscale scores will be assessed from baseline to Week 4.

The Korean version of the Eating Expectancy Inventory (EEI) assesses expectancies regarding the psychological and emotional consequences of eating. The questionnaire consists of 28 items rated on a 7-point Likert scale from 1 to 7, yielding a total score ranging from 28 to 196. Higher scores indicate stronger endorsement of eating-related expectancies. Change in the EEI total score will be assessed from baseline to Week 4.

The Korean version of the Anticipated Effects of Food Scale (AEFS) assesses anticipated emotional responses to eating food. The negative affect subscale for junk food consists of 12 items rated from 1 to 6, yielding a total score ranging from 12 to 72. Higher scores indicate stronger anticipated negative emotional effects of eating junk food. Change in the subscale score will be assessed from baseline to Week 4.

The Korean version of the Anticipated Effects of Food Scale (AEFS) assesses anticipated emotional responses to eating food. The positive affect subscale for junk food consists of 12 items rated from 1 to 6, yielding a total score ranging from 12 to 72. Higher scores indicate stronger anticipated positive emotional effects of eating junk food. Change in the subscale score will be assessed from baseline to Week 4.

The Korean version of the Anticipated Effects of Food Scale (AEFS) assesses anticipated emotional responses to eating food. The negative affect subscale for healthy food consists of 12 items rated from 1 to 6, yielding a total score ranging from 12 to 72. Higher scores indicate stronger anticipated negative emotional effects of eating healthy food. Change in the subscale score will be assessed from baseline to Week 4.

The Korean version of the Anticipated Effects of Food Scale (AEFS) assesses anticipated emotional responses to eating food. The positive affect subscale for healthy food consists of 12 items rated from 1 to 6, yielding a total score ranging from 12 to 72. Higher scores indicate stronger anticipated positive emotional effects of eating healthy food. Change in the subscale score will be assessed from baseline to Week 4.

The Perceived Stress Scale (PSS) assesses the degree to which situations in one's life are perceived as stressful. For the 10-item version (PSS-10), items are scored from 0 to 4 and summed after reverse scoring the positively stated items, yielding a total score ranging from 0 to 40. Higher scores indicate greater perceived stress. Change in PSS total score will be assessed from baseline to Week 4.

The Pittsburgh Sleep Quality Index (PSQI) assesses subjective sleep quality and disturbances. Seven component scores are summed to yield a global score ranging from 0 to 21. Higher scores indicate poorer sleep quality and greater sleep disturbance. Change in PSQI global score will be assessed from baseline to Week 4.

The Beck Depression Inventory-II (BDI-II) assesses the severity of depressive symptoms. The 21 items are scored from 0 to 3 and summed to yield a total score ranging from 0 to 63. Higher scores indicate greater severity of depressive symptoms. Change in BDI-II total score will be assessed from baseline to Week 4.

The Beck Anxiety Inventory (BAI) assesses the severity of anxiety symptoms. The 21 items are scored from 0 to 3 and summed to yield a total score ranging from 0 to 63. Higher scores indicate greater severity of anxiety symptoms. Change in BAI total score will be assessed from baseline to Week 4.

The Binge Eating Scale (BES) assesses the severity of binge eating symptoms and associated thoughts and behaviors. The scale consists of 16 items, with item responses assigned weighted scores ranging from 0 to 3. The total score ranges from 0 to 46, with higher scores indicating greater severity of binge eating symptoms. Change in the BES total score will be assessed from screening to Week 4.

Daily total energy intake, measured in kilocalories per day (kcal/day), will be assessed using dietary records entered in the FatSecret mobile application throughout the 4-week intervention period.

Daily carbohydrate intake, measured in grams per day (g/day), will be assessed using dietary records entered in the FatSecret mobile application throughout the 4-week intervention period.

Daily protein intake, measured in grams per day (g/day), will be assessed using dietary records entered in the FatSecret mobile application throughout the 4-week intervention period.

Daily total fat intake, measured in grams per day (g/day), will be assessed using dietary records entered in the FatSecret mobile application throughout the 4-week intervention period.

Daily total sugar intake, measured in grams per day (g/day), will be assessed using dietary records entered in the FatSecret mobile application throughout the 4-week intervention period.

Daily saturated fat intake, measured in grams per day (g/day), will be assessed using dietary records entered in the FatSecret mobile application throughout the 4-week intervention period.

Daily dietary fiber intake, measured in grams per day (g/day), will be assessed using dietary records entered in the FatSecret mobile application throughout the 4-week intervention period.