Effect of transcranial direct current stimulation (tDCS) on food craving and eating when using a control method that minimizes guessing of the real vs. control condition.

PURPOSE: Validation of transcranial direct current stimulation (tDCS) to treat obesity is hampered by evidence that participants can distinguish real from the traditional-control condition. Correctly guessing the real condition precludes knowing if it is neuromodulation or expectation that suppresses food craving and eating. Therefore, this study tested the putative efficacy of tDCS to the dorsolateral prefrontal cortex (DLPFC) to reduce food craving and eating when an alternative control condition was used that would be difficult to distinguish from the real condition. METHODS: N = 28 adults with a 26-50 BMI range received a typical 20-min 2 mA current session of tDCS targeting the DLPFC as the real condition and a same duration/current tDCS session targeting the sensorimotor cortex (SMC), a region not expected to affect appetite, as the control. Food image craving ratings, in-lab food consumption, and momentary ratings of physical sensations were measured. RESULTS: DLPFC failed to reduce food craving and consumption compared to SMC stimulation. When interviewed, 71% of participants were unable to guess real from control conditions. Those who guessed DLPFC tDCS as real attributed their guess to increased number and frequency of sensations. However, their sensation ratings during tDCS did not differ between conditions. CONCLUSIONS: The results question if tDCS suppresses craving and eating at all, or if the DLPFC is the best target to do so. The results also indicate that alternate-site constant stimulation as the control method may strengthen the scientific evaluation of tDCS to treat obesity. LEVEL OF EVIDENCE: Level I, experimental study.