Transcranial Stimulation May Quell Cravings in Obese Subjects

Marlene Busko

November 06, 2015

LOS ANGELES — A small, proof-of-principle trial suggests that stimulating the prefrontal cortex in the brain may dampen food cravings and lead to weight loss.

Specifically, five obese volunteers who received 40-minute sessions of anodal transcranial direct-current stimulation that activated the left dorsolateral prefrontal cortex on 3 consecutive days consumed significantly less soda (P = .02) and fat (P = .03) over a 9-day period than if they received a treatment that did not activate this brain region.

They also tended to consume significantly fewer calories (P = .07) and they lost more weight (P = .009) if they received active anodal transcranial direct-current stimulation.

However, this decreased intake of calories and unhealthy foods was not seen in four obese subjects who received sham treatments.

Thus, "the findings support the use of transcranial direct-current stimulation to potentially modify activity of the prefrontal cortex and decrease food intake," said Marci E Gluck, PhD, from the Phoenix epidemiology and clinical research branch, National Institutes of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, in Phoenix, Arizona, presenting the findings at Obesity Week 2015.

The article is also published in the November issue of Obesity.

"Those who received this [active intervention] may have been able to exhibit greater inhibitory control over their food choices, which resulted in decreased intake and healthier choices," Dr Gluck suggested.

Moderator and associate editor in chief of Obesity, Donna H Ryan, MD, from Pennington Biomedical Research Center, Baton Rouge, Louisiana, wanted to know how the intervention would be administered if subsequent research showed that it could provide clinically meaningful long-term weight loss.

"Are people going to walk around with a collar [with electrodes] on their head?"

"There would need to be a lot more studies [to confirm effectiveness], and this is a small sample," Dr Gluck cautioned. However, "this is a modular, movable device, which could be used in a physician's office or at home," much like light-box therapy is used for seasonal affective disorder, she noted.

Could Neuromodulation Alter Food Choice?

With transcranial direct-current stimulation, a constant low current is delivered to the brain area of interest via small electrodes, Dr Gluck explained. "It's easily administered…inexpensive, noninvasive, and painless, with minimal side effects [such as tingling, redness]."

In previous work, the researchers showed that after eating a meal, obese individuals have decreased activation in the left dorsolateral sector of the prefrontal cortex — an area of the brain that is implicated in behavior and reward mechanisms.

They hypothesized that if they could increase the excitability and spontaneous neuronal discharge in this brain region, obese individuals might eat fewer calories and lose weight.

To test this hypothesis, they recruited healthy obese adults to stay in their clinic for 9 days and participate in a double-blind, randomized, sham-controlled procedure.

The study subjects followed a weight-maintenance diet for 5 days; on day 6 they had a glucose tolerance test to rule out diabetes, and on days 7, 8, and 9, upon awakening they received a 40-minute session of transcranial direct-current stimulation or a sham procedure where electrodes were placed over the left dorsolateral prefrontal cortex.

Participants were asked to report side effects at the end of each stimulation session, and these included: scalp burn, tingling, skin redness, sleepiness, trouble concentrating, and mood change. The active group had a higher incidence of skin redness at both visits compared with the sham group (60% vs 4%, P < .05).

During the 3 days that they received the intervention, the subjects could choose food and beverages from an automated vending machine that had been preloaded with 40 healthy and unhealthy foods and beverages they liked but did not love, which was accessible all day.

Participants were instructed to eat as much as they desired and return the empty wrappers and uneaten food. The researchers calculated the subjects' intake of fat, protein, carbohydrates, and total calories for the 3 days.

After 36 subjects had been randomized to receive active or sham treatment, the researchers discovered that they had been placing the stimulation leads the wrong way, so that the subjects had actually received cathodal stimulation (with little effect on neuronal excitability) as opposed to anodal stimulation, which makes the neurons more likely to fire.

The researchers thus invited the subjects to return for a follow-up, repeat experiment.

Nine subjects (three men and six women) returned and were randomized to the same treatment groups: five received active transcranial direct-current stimulation and four received a sham procedure. The subjects had a mean age of 42 and a mean body mass index (BMI) of 38.

First Weight Change With Transcranial Direct-Current Stimulation

As in other studies that use an automated vending machine to determine food and beverage intake, the subjects tended to overeat, but those who received the active neuromodulation tended to overeat to a lesser extent.

The four people who received two sets of sham treatments consumed the same number of calories both times. However, the other five patients consumed 692 fewer calories and lost about 1 kg when they received active transcranial direct-current stimulation vs inactive.

Although transcranial direct-current stimulation has been used successfully in other diseases such as Parkinson's disease, "to our knowledge, this is the first study demonstrating changes in body weight [with this intervention in obese subjects]," Dr Gluck said.

The researchers are conducting a larger, longer study where patients spend 9 days in their center (as in the current study) and then return for sham or active treatment 3 days a week for 4 weeks.

The research was funded by the Intramural Research Program of the National Institutes of Health and the National Institute of Diabetes and Digestive and Kidney Diseases. The authors reports no relevant financial relationships.

Obesity. 2015;23:2149–2156. Abstract

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