Burger, fries and a soda—they’re the all-American fast-food combo. When packaged with enticing names—happy meals, value meals, old-fashioned combos—they present options that appeal to the taste buds but can be misleading and potentially unhealthy, according to researchers at UVA and elsewhere.

Fast-food chains typically present combos as good values with supersized portions. For the companies, they’re efficient. For consumers, they’re less hassle to order.

“We were very much surprised that people chose the combo meal option even when there was no price discount,” says Kathryn Sharpe, a professor in UVA’s Darden Graduate School of Business.

The research showed that people tend to eat what is included in the package—more food than they might have eaten otherwise—and order the combo, even if there is no price savings, because they perceive value.

People also perceive that the package represents an “average meal,” even when it’s at least an extra 100 calories, Sharpe says. As a result, consumers in the study showed an increased consumption of fries and soda, items commonly supersized.

The researchers also concluded that providing nutritional information or taxing certain menu items “does not significantly curb consumers’ desire for fast-food items.”

People would be just as happy with smaller portions in combo meals, researchers concluded, but competition among fast-food chains drives up portion sizes.

“If the entire industry adopted size standards, firms could compete more on price and quality, rather than quantity, ultimately benefitting the customer,” Sharpe says.