Here is the design of a clinical trial:

Official Title: The Effect of Hypocaloric Diet Associated With tDCS on Weight Loss and Metabolic Profile: a Pilot, Double Blind, Randomized, Placebo-controlled Study

Included conditions:
- Prediabetes
- Obesity
- Weight Loss
- Diabetes
- Overweight

Study Armgroups:
- {'label': 'Active tDCS + Diet', 'type': 'ACTIVE_COMPARATOR', 'description': 'The participants will receive active tDCS treatment every day for 5 days per week, a total of 20 sessions. They will also be prescribed a hypocaloric dietary during these 4-week treatment.', 'interventionNames': ['Device: Active tDCS', 'Behavioral: Hypocaloric diet']}
- {'label': 'Sham tDCS + Diet', 'type': 'SHAM_COMPARATOR', 'description': 'The participants will receive sham tDCS treatment every day for 5 days per week, a total of 20 sessions. They will also be prescribed a hypocaloric dietary during these 4-week treatment.', 'interventionNames': ['Behavioral: Hypocaloric diet', 'Device: Sham tDCS']}

Interventions:
- {'type': 'DEVICE', 'name': 'Active tDCS', 'description': 'The anode electrode will be placed over F4 position and the cathode electrode over F3, right and left respectively (using EEG 10/20 system). The electric current will be ramped up until it reaches 2 milliampere (mA), and subjects will be stimulated for 20 min.', 'armGroupLabels': ['Active tDCS + Diet'], 'otherNames': ['Active']}
- {'type': 'BEHAVIORAL', 'name': 'Hypocaloric diet', 'description': 'A hypocaloric dietary prescription and individual counseling from a dietician in order to reduce 3% of their initial weight over 4-week treatment.', 'armGroupLabels': ['Active tDCS + Diet', 'Sham tDCS + Diet'], 'otherNames': ['Diet']}
- {'type': 'DEVICE', 'name': 'Sham tDCS', 'description': 'The electrodes will be placed at the same positions as in active stimulation; however, the device will be turned off after 30 s of stimulation.', 'armGroupLabels': ['Sham tDCS + Diet'], 'otherNames': ['Placebo']}

Primary Outcomes:
- {'measure': 'Weight loss', 'description': '3% weight loss', 'timeFrame': '4 weeks'}

Please estimate the sample size based on the assumption: 
Power of 80%, significance level (α) of 0.05, and an additional 40% of participants to account for possible dropouts.
Sample size
          The sample size was calculated on the basis of a significant reduction in the amount of calories ingested after a single 20-minute session of active tDCS (F1,8Â =â8.4, pÂ =â0.02, Î·p2Â =â0.5) [12]. Three types of analysis were performed using G*Power 3.1.9.2Â® software, considering a power of 80% and an Î± of 0.05, as follows: effect size (f)â=â1.0, 10 subjects; effect size (f)â=â0.8, 12 subjects; and effect size (f)â=â0.6, 20 subjects. In another study, a 14.2% reduction in the amount of calories ingested was observed after 8 consecutive days of active tDCS sessions. The authors considered a medium effect size (d)â>â1.09 as sufficient for their findings [13]. Following these assumptions, a total of at least ten subjects would be required in each group to detect a medium-sized effect. Because of possible dropouts, we will include an additional 40% of participants in this study.