Effective Transcranial Direct Current Stimulation Parameters for the Modulation of Eating Behavior: A Systematic Literature Review and Meta-Analysis

Abstract

ObjectiveThis study aimed to consider the effect of differing transcranial direct current stimulation (tDCS) parameters on eating-related measures and how issues with experimental design (e.g., inadequate blinding) or parameters variation may drive equivocal effects.MethodsLiterature searches were conducted across MEDLINE, PsycINFO, Scopus, and Science Direct. Studies using conventional sham-controlled tDCS to modify eating-related measures in adult human participants were included. A total of 1135 articles were identified and screened by two independent authors. Study quality was assessed using the Risk of Bias tool. Random-effects meta-analyses were performed, with subgroup analyses to determine differences between parameter sets.ResultsWe identified 28 eligible studies; 7 showed low risk of bias, with the remaining studies showing bias arising from issues implementing or reporting blinding protocols. Large variation in applied parameters was found, including montage, current intensity and density, participant and researcher blinding, and the use of online or offline tasks. The application of differing parameters seemed to alter the effects of tDCS on eating-related measures, particularly for current density (g = −0.25 to 0.31), and when comparing single-session (g = −0.08 to 0.01) versus multisession protocols (g = −0.34 to −0.29). Some parameters result in null effects.ConclusionsThe absence of tDCS-mediated change in eating-related measures may be driven by variation in applied parameters. Consistent application of parameters that seem to be effective for modulating eating behavior is important for identifying the potential impact of tDCS. Using the findings of this review, we propose a series of parameters that researchers should apply in their work.

Modulating eating behavior with transcranial direct current stimulation (tDCS): A systematic literature review on the impact of eating behavior traits

“…We acknowledge that our meta-analysis considers the effects of heterogeneous tDCS parameters on eating behaviors. This may account for some variation in effect sizes, and it is important that the above recommendations are met with the use of effective stimulation parameters and appropriate study design (see Beaumont et al 116 ).…”

“…With the aim of improving consistency and identifying a meaningful effect of tDCS, we suggest that future work adhere with the following recommendations: Focus on recruiting participants who are susceptible to hedonic‐driven appetite (e.g., those experiencing frequent food craving or presenting with binge‐type behavior). Recruit participants who have trait susceptibilities for the specific outcome measure of interest (e.g., recruit those with binge eating symptomatology when looking to modulate food reward). To elucidate the potential link between enhanced executive functioning and improved appetite control following tDCS, studies should establish participants' baseline executive functioning capabilities and monitor any changes following stimulation. Limit the information provided to participants during recruitment and screening procedures, as this can drive any effects on eating behavior outcomes. Incorporate a comprehensive group of validated measures, including explicit liking and explicit and implicit wanting. Control fasting duration and measure baseline subjective appetite, even where subjective appetite is not a measure of interest. We acknowledge that our meta‐analysis considers the effects of heterogeneous tDCS parameters on eating behaviors. This may account for some variation in effect sizes, and it is important that the above recommendations are met with the use of effective stimulation parameters and appropriate study design (see Beaumont et al 116 ). Our understanding of population‐based differences in tDCS effects is still limited, and we need more studies to confirm our hypothesis that those with deficits in the control of eating behavior will be responsive to the effects of tDCS.…”