When it comes to restaurant portions, size matters, Penn researcher says

When ordering a drink or fries at a fast food restaurant, we're used to having the option of choosing a size. But what if that was an option for entrées, as well?

Sophia Hua , an assistant professor of medical ethics and health policy at the University of Pennsylvania, sees a missed opportunity. She is researching potential solutions to make dining out healthier in a nation where nearly 75% of adults living in the U.S. are either overweight or obese .

Hua recently completed a real-world experiment at two cafeterias (not in Philadelphia), where students, staff, and guests received the option of portion sizes at different prices. Hua and her team are analyzing the data now, to determine if this leads to fewer calories purchased — and more revenue for the cafeteria. "That's something that the restaurant owners that I've spoken to really want to understand," she said.

Research shows smaller portions is something many Americans want . Yet at most restaurants, it's not an option — and the only size offered is getting larger and larger.

In recent decades, the amount of food served per portion at restaurants has grown significantly . Among many processed foods, portions are up to five times bigger than when those foods were first introduced.

And we aren't leaving behind more leftovers as a result. Research consistently shows that people eat what's on their plate, even if it's more than they're hungry for. One study found that, when people were given 50% more food for eleven days straight, they ate it — consuming an additional 400 calories per day .

Creating portion size options allows people to still indulge in their favorite foods, Hua said, just not overindulge.

"The research does show that people are interested in smaller portions," she said. "There is a demand for this, but for the most part, I don't think people think a ton about portion sizes. They kind of eat what's laid out in front of them."

The landscape Some restaurants are starting to try it: Cheesecake Factory, for instance, has menu options it calls "SkinnyLicious."

But for now, portion options at major restaurants are the exception, not the rule — which is a missed opportunity, noted Hua. "If [restaurants are] constantly only offering larger portions, you're missing that fairly large segment of the population that would be very happy with these smaller portions."

What matters most to restaurants is their bottom line, she said. Although it might seem like restaurants would save money by serving less food, larger portions don't cost much more to restaurants — much of a restaurant's costs are fixed, such as staffing , which won't change if they offer smaller portions. Plus, if restaurants offer two portion sizes of the same entrée, they have to charge less for the smaller portion, which is lost money, said Hua.

Still, she believes offering portion sizes can ultimately save restaurants money. Smaller portions cut down on food waste, "something that a lot of restaurants are very wary of," and may bring more customers. "There's a portion of this population that sees a 1,000-calorie item on a menu and might not even go to that restaurant. But if they see that they have an option to get something that's 500 calories, they might think, alright, this is the restaurant that I can go to."

Giving customers the option of a smaller portion is also the right thing to do, Hua added. In a recent opinion for the health news site STAT, Hua called smaller portions a form of "harm reduction," a term used for public health interventions that reduce the harm associated with drug use , such as needle exchange services. "We're saying to have less of what you want to have as a way to still get what you want, while hopefully lessening those health impacts."

In the meantime, since most Americans don't have the option of portion sizes when they eat at restaurants, Hua recommended a few workarounds: Avoid all-you-can-eat buffets, stick to appetizers, order an entrée to share with someone else, or ask the server to pack up half of their entrée to-go, so they can take it home. "It takes more than just willpower" to resist the temptation of large portions, she said.