May 10, 2017

‘Dual self’ study explores why people make unhealthy food choices

by Andrea Hahn

CARBONDALE, Ill. – If you want to eat healthy, you’ll have to listen to your orbitofrontal cortex and tell that amygdala to take a rest. 

Jeb Asirvatham, assistant professor of agribusiness economics at Southern Illinois University Carbondale, is interested in what makes people overeat, or make unhealthy food choices, when they ought to know better. He could have focused his study on surveys or observations of people’s eating habits. Instead, he studied research involving brain MRIs involving decision-making. His objective was to apply the science to a model for human diet decisions.   

His preliminary findings have to do with understanding the “dual self,” the phenomenon wherein a person makes choices they know are not beneficial. In this case, the “dual self” refers to how a person who has at least some knowledge of nutrition and calories will make healthy food choices in some settings, but then, in other settings, make poor choices, even when healthier choices are available. 

According to basic neuroscience and putting it very simply, when we make choices that involve forethought, conscious calling-upon of experience and learning, we are using the orbitofrontal cortext. When we act on impulse as a response to pleasure or fear, that’s the amygdala talking. When it comes to food choices, the orbitofrontal cortext is that part of the brain reminding us about calories and nutrition – the long-term aspects of diet choice. The amygdala is the part that has us grabbing the brownie or the extra-helping without even thinking about it. This duality is called “intrapersonal conflict.” 

Anyone who has ever tried to diet understands the limits of willpower, Asirvatham said. When we find ourselves at conflict, which happens when the amygdala urges behavior the orbitofrontal cortext discourages, we become unhappy. It’s one of the things that makes dieting unpleasant and difficult to maintain. 

So, what if we could be more aware of which food choice situations stimulate the amygdala? Would that make healthy decision-making easier? Asirvatham, and colleague Wanki Moon, professor of agribusiness economics, are working on a model to find some answers. 

“People love to eat,” Asirvatham said. “We don’t eat only for sustenance; we eat for enjoyment. So one thing we have to factor in is choice. In order to stick to a diet, you have to make sure you like and enjoy eating some of the foods in your diet. There must be some satisfaction derived from eating besides just being full or meeting nutritional needs.” 

This is why institutional menus, such as school lunch programs, fail or lead to food waste when they don’t account for preference and foods that people generally like to eat, namely, those with fats and sugars. While we might consciously understand that broccoli is healthier without cheese sauce, the part of our brain that craves fats and sugars wants that cheese sauce and signals accordingly. Thus it’s not a character flaw that makes people give in to cravings. It’s the amygdala. 

Asirvatham also explored why people continue to eat even when they are consciously aware that they do not need more nutrition. The level of enjoyment in eating generally decreases as we eat – except when it doesn’t. There are times when the impulse part of the brain overrides the sensible part of the brain that says “nutritional needs are met” or “feeling full now.” 

To explore why this happens, Asirvatham used models showing dietary outcomes or choices under different scenarios. For example, one model compares a dining situation resembling a buffet, where there are many food choices and none of them are individually priced, with an opposing scenario in which each food item is individually priced. 

“You want to get your money’s worth at a buffet, so you may eat more than you actually want,” Asirvatham said. “Also, because there are so many choices at a buffet, generally, you can choose different tastes rather than eating only one thing and growing satiated with the taste of that one thing.” 

Basically, he said, the structure of the buffet meal rewards the amygdala, making it harder for the orbitofrontal cortex to engage analytical decision-making. He’s found that something as simple as ordering off a menu with individual entrees and individual prices tends to reduce intake. In other words, when a person has to select one item from a menu instead of from an array of prepared food, it’s easier to focus on benefits such as nutrition rather than solely focusing on the immediate benefit of taste. 

Asirvatham and Moon presented some of the early findings in a paper titled “A Dual-Self Theory of Dietary Behavior and Health Outcomes” last fall at the Missouri Valley Economics Association meeting. 

“We’re at the final stages in modeling to determine how people choose foods based on their perception of the health of the food choice versus the pleasure in eating it, and the health effects of the food and the cost of it,” Asirvatham said. 

“We live in a world of free refills and foods that are better bargains as we ‘super-size,’ and that’s a problem,” he said. “But we’ve found that when people refer to a menu with individually priced entrees, they are better able to balance what they like -- the fat and sugar content foods -- with the cost, both in dollars and in nutritional value.” 

Jeb Asirvatham is available to talk about models for human diet decisions, why people overeat, the role food choice and menu play in healthy eating, and peer pressure and food choice, among other topics. Contact him at