When people are given a smorgasbord of options to eat, like at a buffet or a Super Bowl party, the temptation to sample most of the spread is often too great to resist. That link between variety and overeating is now backed by research that helps explain the urge to indulge.

Researchers at Penn State University designed a study to test the appetites of people presented with varying amounts and types of food. But instead of offering them real food, the researchers gave virtual reality headsets to people in the study to stack their plates in a simulated environment.

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“It is costly and wasteful to make an entire buffet so that a single participant can use it at mealtime, especially if that participant needs to go through the buffet multiple times, like in this study,” Travis Masterson, an assistant professor of nutritional sciences, said in a news release. “And when we need a different setup, it is much easier to change a setting in VR than it is to alter the amount of food on a buffet.”

Masterson’s past research demonstrated that people make similar choices in real and virtual reality buffets. The latest study, published in the journal Appetite, sought to find out what drives people to eat more food — and make less healthy choices — when presented with a surplus of options.

More than 2 in 5 U.S. adults over 20 are considered obese, according to the U.S. Centers for Disease Control and Prevention, and about 9% are severely obese. Millions of Americans living at unhealthy weights develop chronic conditions, including diabetes and heart disease, that often stem from their diets and relationships with food.

Masterson and his colleague, John Long, recruited 50 people ages 18 to 65 to come to their lab for three sessions. When they put on the VR headsets for each visit, they were placed at buffets with either nine, 18 or 27 choices of food. The buffets had a roughly equal mix of high-calorie sweets, like cookies, and healthier choices like vegetables during each visit. All participants were told not to eat, exercise or drink for several hours before their visits to ensure they came hungry.

Once inside the virtual buffet, people were given free rein to pack their plates with as much as they wanted as many times as they wanted. The combined weight and calories of the foods they chose were totaled for each visit.

When the virtual buffet had only nine items, the study participants selected foods totaling about 850 calories. When there were 18 options, people filled their plates with 1320 calories of food — a 55% increase. With 27 options, calories increased to an average of nearly 1,500 — 75% higher than when people only were offered nine items. 

Even though the total weight of foods chosen tended to have an upper limit in grams, cravings for less healthy foods kicked in when more options were available.

“People became more likely to choose higher calorie-dense foods,” said Long, the study’s first author, who’s a postdoctoral scholar in food science and nutritional sciences. “In the U.S., many people consume more calories than they need, and the wide variety of foods in our environment may nudge us to eat more than we otherwise would.”

The study examined whether any of five personality traits — openness, extraversion, agreeableness, neuroticism and conscientiousness — had any effect on the decisions people made at the virtual buffet. Only conscientiousness, which is associated with self-discipline and goal-setting, had any correlation with what people chose. Those with higher scores for conscientiousness added fewer high-calorie foods than people with lower scores.

The researchers noted that eating habits are often shaped by our environments, from buffets and college dining halls to supermarkets that offer vast selections of healthy and unhealthy foods.

“If we identify the aspects of our modern food environment — excessive variety, slick packaging, processed foods and more — that increase how much people eat, we can redesign our environment to help us make healthier food choices,” Long said.