Disgust Diet: Can You Train Your Brain To Recoil At High-Calorie Foods?

Some days, the french fries are just irresistible. You know it's not the best thing to put in your body, but did that salad really stand a chance after the smell of fried garlic, Parmesan and thyme on crisp potato wedges wafted over to you?

Well, Kristina Legget, a psychologist at the University of Colorado Denver Anschutz Medical Campus, thinks she can muffle that siren song. In a new study, she suggests there could be a simple way to retrain people's brains into making fries or ice cream or anything else suddenly seem unappealing — even a little disgusting.

It's a tool that psychologists call subliminal priming, which works kind of like a Jedi mind trick. It subconsciously implants an idea into someone's mind that influences how they react to whatever comes next. It could be a whisper in the background or a word that rhymes with something you're supposed to choose.

In this case, Legget and her colleagues showed 42 volunteers a picture of a high-calorie food like french fries or hoagies and asked them, "How much would you like to eat this right now?" (Very much, they said.) Then she flashed volunteers a disgusting image, like a picture of ants crawling over pizza or a mutilated leg.

After judging a food picture's appeal, ​study participants focused on a blank screen for 500 milliseconds, then were flashed with a disgusting image for 20 milliseconds before being shown an image of food again. To them, it looked as though the blank screen went directly back to the photo of food.

Legget et al. 2015 American Journal of Clinical Nutrition​

The flash was fast enough that the subjects wouldn't be able to consciously recognize the picture, but slow enough to signal a part of the brain called the amygdala — which is "sort of like a memory for emotional systems," explains Dr. Alain Dagher, a neurologist at McGill University in Montreal who was not involved in the study. "The amygdala detects [the picture] very rapidly before it gets to consciousness and then activates the appropriate emotions."

With their amygdalas fired up with feelings of disgust, volunteers again saw photos of high-calorie foods. But this time, they didn't want to eat the foods as badly as before the flash. Their minds were still churning with that phantom repulsion, and those effects lasted, Legget's team reports in the current issue of the American Journal of Clinical Nutrition.

"Three to five days later, they showed the same reduction [in desire] for the high-calorie food as they did immediately after the intervention," Legget says. That suggests the volunteers' brains had actually linked disgust to that type of food, and the association wasn't limited to the moment.

"It's a very interesting finding, you know, the ability to change the value, basically, of a food item using this sort of subliminal priming," Dagher says. In the past, scientists and health researchers have tried putting more information on nutritional labels and educating people on what foods are healthful or unhealthful in an effort to fight obesity. "That doesn't seem to work — doesn't seem to get people to eat healthy foods, as we know," Dagher says.

Legget thinks the "disgust" technique could be used to help people make healthier food choices automatically. She's hoping there could be a DIY program, where people could go online and rewire their brains to dislike fatty foods. "You know, we've looked into maybe developing an app or something like that," she muses. "It could work." She imagines people might use the phone app occasionally to target foods that they have trouble stopping themselves from eating. In other words, if people prime their brains this way, the next time they're faced with garlic cheese fries, they might not want them as much. It'll be easier to pick the salad.

Others are less optimistic. "Obviously, as a therapy, it really wouldn't work," Dagher says. "I don't think I could imagine a situation where you just make people disgusted by every single high-calorie food." The problem is the technique only works with one type of food at a time. Make ice cream look nasty? Well, maybe you switch to chocolate mousse. And, Dagher adds, you might just get over your disgust later.

And there's no guarantee that just because the ice cream feels less seductive, you'd actually eat less of it. The study didn't show whether people's behavior changed. "You have this battle going on in your brain, this little weak effect of subliminal priming, versus the very strong rewarding value of the substance," Dagher says. "There are powerful forces you have to fight against." In other words, maybe ice cream is just too luscious.

The other problem? If you try to use the tool as a therapy, then patients would be aware they're being primed. That defeats the purpose of subliminal messaging, says Jennifer Harris, a social psychologist at the University of Connecticut. "If people are aware of the stimuli, they'll be able to counteract the effect with a conscious effort," she says.

Besides, billboards, Internet banners and TV ads nudge us to want calorific foods every day, Harris says. Those messages are so pervasive, so inescapable, it's doubtful that one short-term prime could counteract that.