To that end, Dr. Elizabeth Capaldi Phillips, the lab’s principal investigator, is shepherding the research of post-doctoral fellow Dr. Devina Bajaj and Ph.D. candidate Lynn Wilkie on the psychology of food – why we love it, hate it, and eat the amount we do. They hope to create a cultural change by combining psychology and nutrition to address health concerns, for both the clinically obese and the average person who wants to live healthier or lose a few pounds. Bajaj dreams of partnering with weight-loss institutes to put their work into life-saving application. Capaldi Phillips would like to see their findings, which have been published in scientific, peer-reviewed journals, implemented in school lunch programs. It all begins with education, they say.
“You can learn to like the foods that you hate – assuming you want to. A lot of people are happy with the foods they hate,” Capaldi Phillips says. “People assume that your likes and dislikes are built in, they’re genetic, and that’s the way it is. Very little is genetic.”
Biologically, humans are designed to like sweet and salty and dislike sour and bitter. The evolutionary rationale: Sweet and salty flavors indicate freshness in the wild, while sourness and bitterness accompany spoilage and poisonous plants. These preferences cross cultures and species. People in France and Fiji have the same facial reactions to flavors – lip-smacking smiles for sweetness and salt, sputtering grimaces for sour and bitter – as the rats studied in the lab. Those predilections, and the phenomenon of the “supertaster” (people who taste more intensely due to a higher number of papillae in their taste buds; they make up 25 percent of the world’s population), are the only genetic components of eating habits. Everything else is learned.
“Eating is another habit. Every time you eat, you’re doing a learning trial and teaching yourself to eat in a certain way,” Capaldi Phillips says. “Let’s say you eat candy. You’re pairing fat with sweet, because that’s what candy is. You’re learning to like fat.”
Training someone to like a certain food – say, those bitter but healthy sprouts – can be achieved by exposure (acceptance comes after 10 exposures and enjoyment after 20) or by two pairing techniques: flavor-flavor and flavor-calorie. The lab employs both in its trials on college students and preschoolers. Boiled veggies served plain usually elicit a negative reaction. When the veggies are topped with a non-nutritive sweetener or dipped in cream cheese, however, the majority of subjects report favorable reactions. Toppings are gradually tapered until subjects enjoy the vegetables unadorned.
Many aversions stem from neophobia, or fear of newness. Infants eat and enjoy almost anything until they hit age two, Capaldi Phillips says. After that, new food is greeted with wariness; many purported aversions are to foods people have never tried. Some aversions stem from trauma – getting sick after eating something, ingesting something spoiled or while experiencing stress, etc. “You can think yourself into an aversion as well. You can do this cognitively; you don’t have to actually experience it,” she says. Many vegetarians are cognitively averse to meat because of their moral disgust, and anorexics cognitively condition themselves to be fat-averse.
Bajaj studies the factors that affect how much people eat. Using the Delboeuf illusion (see illustration), Bajaj has found that people eat less food when it’s cut into many pieces, even if it’s the same amount as in a single-piece serving. She observed this in the rat test population and found it was true for humans, too. “It may have something to do with surface area... something cut into pieces might [appear to] occupy more room on the plate.”
This illusion can help you eat less in general, but can also help you cut down on unhealthy foods. Breaking a cookie into many pieces or cutting a slice of cake into smaller segments can prevent over-indulging, Bajaj says. “Registered dieticians will tell you, ‘Change your diet. Eat less fat,’” Bajaj says. “It’s easy to say it, but when you actually have to do it [it’s more difficult]. And that’s where we come in. We can get people to change.”
Hate on the Plate
The most common aversions encountered at Arizona State University’s Conditioned Feeding Lab:
Meat – The flesh and blood factors freak out more than vegetarians. It’s the No. 1 reported aversion.
Mushrooms– A spongy texture and woodland flavor make fungi a bit too funky for many.
Tomatoes – Grainy, pulpy, fleshy, drippy: A tomato is a texture-freak’s worst nightmare.
Bitter things – Veggies, leafy greens, coffee and beer are bitter pills for palates hardwired to prefer sweet things.
Spicy foods – Many people just can’t handle the heat, especially if their mothers never ate spicy things while pregnant and nursing.
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