On Tuesday, the Food and Drug Administration releases rules requiring an additional set of food merchants to disclose caloric content: theaters, amusement parks, convenience stores, pizza chains, and grocery store prepared food sections.

Today, Americans spend half their food dollars outside the home, and consume around 30 percent of their calories outside. Strikingly, when children eat out, their calorie consumption doubles.

Does transparency change behavior? One of the largest studies on this followed Starbucks users, at stores with calorie signs and without.

“People were systematically underestimating their calories in food items,” says study co-author Bryan Bollinger, who teaches marketing at Duke University. “So when they saw the information on the board, they were surprised and then reacted accordingly. Consumers can and will use this information if it’s useful to them.”

Listen here for more from Bollinger’s interview:

The study found purchased calories fell an average 6 percent, and that changes in behavior stuck with Starbucks consumers, even when they visited outlets without calorie signage.

There’s also evidence that merchants required to post calorie counts start to offer more low-fat choices.

These finalized FDA arise from the Affordable Care Act and are scheduled to take effect in one year.