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

Repeated net-tDCS of the hypothalamus appetite-control network enhances inhibitory control and decreases sweet food intake in persons with overweight or obesity

BACKGROUND

Reduced inhibitory control is associated with obesity and neuroimaging studies indicate that diminished prefrontal cortex activity influence eating behavior and metabolism. The hypothalamus regulates energy homeostasis and is functionally connected to cortical and subcortical regions especially the frontal areas.

OBJECTIVES

We tested network-targeted transcranial direct current stimulation (net-tDCS) to influence the excitability of brain regions involved in appetite control.

METHODS

In a randomized, double-blind parallel group design, 44 adults with overweight or obesity (BMI 30.6 kg/m2, 52.3 % female) received active (anodal or cathodal) or sham 12-channel net-tDCS on the hypothalamus appetite-control network for 25 min on three consecutive days while performing a Stop-Signal-Task to measure response inhibition. Before and after stimulation, state questionnaires assessed changes in desire to eat and food craving. Directly after stimulation, participants received a breakfast buffet to evaluate ad-libitum food intake. An oral glucose tolerance test was conducted at follow-up. Resting-state functional MRI was obtained at baseline and follow-up.

RESULTS

The Stop-Signal Reaction Time (SSRT) was shorter in both active groups versus sham, indicating improved response inhibition. Additionally, a stronger increase in hypothalamic functional connectivity was associated with shorter SSRT. Caloric intake of sweet food was lower in the anodal group versus sham, but no main effects between groups were observed on total and macronutrient intake, food craving ratings and desire to eat. At follow-up, no differences were observed between groups on peripheral metabolism.

CONCLUSION

Our study suggests that modulating hypothalamic functional network connectivity patterns via net-tDCS may improve food choice and inhibitory control.

Effective non-invasive brain stimulation over dorsolateral prefrontal cortex for modulation of food craving and consumption: A systematic and meta-analytic review

In recent decades, non-invasive brain stimulation (NIBS) has gained attention as a potential tool for promoting dietary regulation by modulating activity in the dorsolateral prefrontal cortex (dlPFC). However, the findings from individual experimental studies and meta-analyses have been inconsistent. To address this, we conducted a meta-analytic and systematic review of past studies focusing on neuromodulation of the dlPFC. Our research included 13 studies using repetitive transcranial magnetic stimulation (rTMS; 16 samples, 506 participants) and 29 transcranial direct current stimulation (tDCS; 31 samples, 1004 participants). By adjusting the pre-post correlation, we detected small-to-moderate effect sizes of NIBS on food craving (rTMS: Hedge's g = -0.57; tDCS: Hedge's g = -0.26) and food consumption (rTMS: Hedge's g = -0.51; tDCS: Hedge's g = -0.17). Additionally, we observed that the efficacy of NIBS was influenced by various moderators, including stimulation parameters, research protocols, and participant characteristics. Notably, both rTMS and tDCS appeared to enhance dlPFC function in dietary regulation for people with eating disorders or obesity. Furthermore, these effects were more pronounced with multi-session stimulation compared to single-session stimulation. Finally, based on the existing literature, we discuss the role of the dlPFC in the appetitive reward processing pathway and provide suggestions for future research directions.

Enhancing the outcomes of bariatric surgery with inhibitory control training, electrical brain stimulation and psychosocial aftercare: a pilot study protocol

BACKGROUND

Notwithstanding the documented short- and long-term weight loss and remission of physical and mental diseases following bariatric surgery, a significant proportion of patients fail to respond (fully) to treatment in terms of physical and mental health improvement. Mounting evidence links food-specific impulsivity, prefrontal cortex (PFC) hypoactivity and disrupted hormone secretion in bariatric surgery candidates to poorer post-surgical health outcomes. Neuromodulatory treatments like transcranial direct current stimulation (tDCS) uniquely target these neurobehavioral impairments. We present a pilot study protocol offering tDCS combined with an inhibitory control training and a structured psychosocial intervention to patients after bariatric surgery.

METHODS

A total of N = 20 patients are randomized to 6 sessions of verum or sham tDCS over the PFC, combined with an individualized food-specific inhibitory control training and a structured psychosocial intervention within 18 months after bariatric surgery (t0). Beyond acceptability, feasibility and satisfaction of the intervention, effects of verum versus sham tDCS on food-specific impulsivity and on secondary outcomes quality of life, general impulsivity and psychopathology, food-related cravings, eating disorder psychopathology, weight trajectory and endocrine markers are assessed 4 weeks (t1) and 3 months after the intervention (t2).

DISCUSSION

Results will provide information on the potential of combining tDCS with an inhibitory control training and a structured psychosocial intervention to enhance physical and mental outcomes after bariatric surgery. The present study may guide the development of future research with regard to tDCS as a brain-based intervention and of future post-surgical clinical programs, paving the way for randomized-controlled trials in larger samples.

TRIAL REGISTRATION

The trial was prospectively registered on July 8, 2024, under the registration number DRKS00034620 in the German Clinical Trials Register ( https://drks.de/search/de/trial/DRKS00034620 ).

No effect of prefrontal transcranial direct current stimulation (tDCS) on food craving, food reward and subjective appetite in females displaying mild-to-moderate binge-type behaviour

Previous work suggests there may be an effect of transcranial direct current stimulation (tDCS) on appetite control in people at risk of overconsumption, however findings are inconsistent. This study aimed to further understand the potential eating behaviour trait-dependent effect of tDCS, specifically in those with binge-type behaviour. Seventeen females (23 ± 7 years, 25.4 ± 3.8 kg m-2) with mild-to-moderate binge eating behaviour completed two sessions of double-blind, randomised and counterbalanced anodal and sham tDCS applied over the right dorsolateral prefrontal cortex at 2.0 mA for 20 min. Subjective appetite visual analogue scales (VAS), the Food Craving Questionnaire-State (FCQ-S), and Leeds Food Preference Questionnaire (LFPQ) were completed pre- and post-tDCS. Participants then consumed a fixed-energy meal, followed by the VAS, FCQ-S and LFPQ. No difference between pre- and post-tDCS scores were found across fullness (p = 0.275, BF10 = 0.040), prospective consumption (p = 0.127, BF10 = 0.063), desire to eat (p = 0.247, BF10 = 0.054) or FCQ-S measures (p = 0.918, BF10 = 0.040) when comparing active and sham protocols. Only explicit liking and wanting for high-fat sweet foods were significantly different between conditions, with increased scores following active tDCS. When controlling for baseline hunger, the significant differences were removed (p = 0.138 to 0.161, BF10 = 0.810 to 1.074). The present data does not support the eating behaviour trait dependency of tDCS in a specific cohort of female participants with mild-to-moderate binge eating scores, and results align with those from individuals with healthy trait scores. This suggests participants with sub-clinical binge eating behaviour do not respond to tDCS. Future work should further explore effects in clinical and sub-clinical populations displaying susceptibility to overconsumption and weight gain.

Effect of transcranial direct current stimulation on homeostatic and hedonic appetite control and mood states in women presenting premenstrual syndrome across menstrual cycle phases

PURPOSE

This study investigated the acute effect of anodal transcranial direct current stimulation (a-tDCS) over the left dorsolateral prefrontal cortex (DLPFC) on appetite, energy intake, food preferences, and mood states in the luteal and follicular phases of the menstrual cycle in women presenting premenstrual syndrome.

METHODS

Sixteen women (26.5 ± 5.2 years; 1.63 ± 0.1 m; 64.2 ± 12.8 kg; body mass index 24.0 ± 5.0 kg/m²; body fat 27.6 ± 7.5%) with the eumenorrheic menstrual cycle were submitted to a-tDCS and sham-tDCS conditions over their follicular and luteal phases. At pre - and post-tDCS, hunger and desire to eat something tasty, (analogic visual scale), the profile of mood states (POMS), and the psychological components of food preferences (Leeds Food Preference Questionnaire-BR) were assessed. Participants recorded their food intake for the rest of the day using a diary log.

RESULTS

There was a trend towards main effect of condition for decreased implicit wanting for low-fat savory food after a-tDCS but not sham-tDCS regardless of menstrual cycle phase (p = 0.062). There was no effect for self-reported hunger, desire to eat, energy and macronutrient intake, and on other components of food preferences (explicit liking and wanting for low- and high-fat savory and sweet foods, implicit wanting for low- and high-fat sweet and high-fat savory food); as well as for mood states.

CONCLUSIONS

Although no significant effects of a-tDCS were found, the present investigation provides relevant perspectives for future studies.

Effects of neuromodulation on executive functions and food desires in individuals with obesity: a systematic review

Introduction

Objective: to describe the effects of neuromodulation on the performance of executive functions in overweight and/or individuals with obesity. Methods: articles published in PubMed, ScienceDirect, BIREME, and Web of Science databases were selected using the following combination of descriptors: ("problem solving" OR "executive function" OR memory) AND (tDCS OR TMS) AND obesity. After applying the selection criteria, 08 articles were included for analysis. Results: the articles included had an average of 30.1 participants per study, with a minimum of 12 and a maximum of 76. The overall nutritional status ranged from underweight to grade 3 obesity, and the general mean body mass index was 28,1 kg/m2. Regarding the instruments used to assess executive functions, the most frequent were: the flanker paradigm; binocular rivalry for Continuous Flash Suppression (bCFS/NoCFS); Stroop task; Go/No-Go task; and N-back task. The primary outcomes were dependent on the neuromodulation target site. Reduced food craving and improved performance in the active group were observed from decreased response time and increased precision in cognitive tasks. Conclusion: neuromodulation can generate changes in executive functions, reducing food cravings in overweight and individuals with obesity.