OBJECTIVE Obesity is associated with decreased activity in the prefrontal cortex. Transcranial direct current stimulation (tDCS) modifies cortical excitability and may facilitate improved control of eating. We measured energy intake (EI) and body weight in subjects who received cathodal vs. sham (study 1) and subsequent anodal vs. sham (study 2) tDCS aimed at the left dorsolateral prefrontal cortex (LDLPFC). METHODS Nine (3m,6f) healthy volunteers with obesity (94±15kg [M±SD]; 42±8y) were admitted as inpatients for 9d to participate in a single-blind, randomized, placebo-controlled crossover experiment. Study 1: following 5d of a weight-maintaining diet, participants received cathodal or sham tDCS (2mA, 40min) on 3 consecutive mornings and then ate ad libitum from a computerized vending machine, which recorded EI. Weight was measured daily. Study 2: participants repeated the study, maintaining original assignment to active (this time anodal) and sham. RESULTS Participants tended to consume fewer kcal/d (p=0.07), significantly fewer kcal from soda (p=0.02) and fat (p=0.03) and had a greater %weight loss (p=0.009) during anodal v. cathodal tDCS. CONCLUSIONS These results indicate a role for the LDLPFC in obesity and food intake. This proof of concept study suggests, for the first time, the potential application of anodal tDCS to facilitate weight loss.

BackgroundObesity is the result of chronic positive energy balance. The mechanisms underlying the regulation of energy homeostasis and food intake are not understood. Despite large increases in fat mass (FM), recent evidence indicates that fat-free mass (FFM) rather than FM is positively associated with intake in humans.MethodsIn 184 humans (73F/111M; age 34.5±8.8y; % body fat [PFAT] 31.6±8.1%) we investigated the relationship of FFM index (FFMI kg*m2), FM index (FMI kg*m2;), and 24-hour energy expenditure (EE, n=127) with ad-libitum food intake using a 3d vending machine paradigm. Mean daily calories (CAL), and macronutrient intake (PRO, CHO, FAT) were determined and used to calculate the relative caloric contribution of each (%PRO, %CHO, %FAT) and percent of caloric intake over weight maintaining energy needs (%WMEN).ResultsFFMI was positively associated with CAL (p<0.0001), PRO (p=0.0001), CHO (p=0.0075), and FAT (p<0.0001). This remained significant after adjusting for FMI. Total EE predicted CAL and macronutrient intake (all p<0.0001). FMI was positively associated with CAL (p=0.019), PRO (p=0.025) and FAT (p=0.0008). In models with both FFMI and FMI, FMI was negatively associated with CAL (p=0.019) and PRO (p=0.033). Both FFMI and FMI were negatively associated with %CHO and positively associated with %FAT (all p<0.001). EE and FFMI (adjusted for FMI) were positively (EE p=0.0085; FFMI p=0.0018) and FMI negatively (p=0.0018; adjusted for FFMI) associated with %WMEN.ConclusionFood and macronutrient intake is predicted by FFMI and to a lesser degree by FMI. FFM and FM may have opposing effects on energy homeostasis.