Dining out was once reserved for the wealthy or a special occasion. Not anymore. Now more than a third of the food Americans eat is made up of so-called “away-from-home” foods, which include both restaurant food and pre-packaged or prepared foods purchased at supermarkets. And about 40 percent of that comes from fast-food restaurants serving the likes of cheeseburgers and French fries.

Driven in part by a desire to better understand the obesity epidemic in America, Alice H. Lichtenstein, a senior scientist at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts, and her colleagues looked at whether portion sizes and the nutritional content of fast food have changed over the last two decades. They gathered data from the three most popular fast-food chains in the United States between 1996 and 2013. They tallied the sodium, saturated fat and trans fat content in French fries, cheeseburgers and grilled chicken sandwiches.

Perhaps surprisingly, they found that neither portion size nor nutritional content has changed much over 17 years—but, they stress, that doesn’t mean the food is healthy. Fast-food portion sizes are still quite large, they say, and often contain sky-high amounts of salt and many more calories than most of us need at one sitting.

While the nutritional content of the foods varied markedly among the restaurants—a small serving of fries at one chain might contain more than twice as much sodium as the same product at another chain—the scientists found a large serving of fries at all three chains contains about a quarter of an active adult’s daily recommended calories. Likewise, a large meal of a cheeseburger, fries and a soda contains almost a full day’s recommended serving of sodium.

The team’s findings were published on Dec. 31 in a pair of papers in Preventing Chronic Disease, the research journal of the U.S. Centers for Disease Control and Prevention.

Tufts Now asked Lichtenstein, who is also the Stanley N. Gershoff Professor of Nutrition Science and Policy at the Friedman School, about the implications of their findings.

Tufts Now: What’s the bottom line that comes out of these two studies?

Alice Lichtenstein: The take-home message is that we can’t just attribute the obesity epidemic to the simple, knee-jerk explanation of portion size. Certainly there is evidence that portion sizes were increasing in the late 1990s and early 2000s. But what we’ve found is they’ve actually stabilized. We’ve also found that simple advice to individuals—to always order the small portion, for example—may not necessarily have the intended effect. That’s because the small size of an item in one fast-food outlet can be very different from the small size of the same item in another fast-food outlet, whether we’re talking about sodium content or calories.

The other point is that the calories, saturated fat and sodium in cheeseburgers, fries and regular beverages are extremely high and represent a very large proportion of what somebody should be consuming over an entire day.

That’s why I’m a very strong proponent of having the nutrition information, particularly for the over-consumed nutrients that are linked to chronic disease risk—calories, sodium and perhaps saturated fat—posted at the point of purchase.

Is posting nutrition information enough to encourage consumers to make healthy choices?

We really need to get the message across that not only should this information be used, but that it should be used wisely. If somebody sees that there are 1,200 milligrams of sodium in an item, what does that mean? How would they know whether they are supposed to consume 2,300 milligrams—the recommended amount for most people—over the course of the day or 10,000 milligrams?

If they see that an item has 750 calories, again, what does that mean? Unless one knows that the average adult needs about 2,000 calories per day, the information isn’t in context. Hence, there are limitations about how useful it is. We need to provide the information, but more importantly, we really need to educate people about how to use the numbers.

How would you go about educating people?

I would absolutely start with mandatory food and nutrition education in elementary school up through high school. That would help kids understand how to use nutrition labels. For example, if you have 400 milligrams of sodium in a certain item, how much does that represent for the upper daily limit? That type of information can be incorporated into a health class, math class or science class.

I’d also include a strong educational component in terms of basic cooking skills. Then when these children become young adults, they won’t have to feel dependent on fast-food restaurants or other places to prepare their food, because they will have the skills to purchase and prepare food on their own. I call it hunting and gathering in the 21st century.

But we can’t just rely on educating children. Once mandatory nutrition labeling goes into effect, I think we need strong public health campaigns to put the numbers into perspective, and then we need to give it time. It takes a long time for this kind of information to get ingrained in the population.

Would you be in favor of public health legislation for things such as lower sodium levels in fast food?

I’m a very big proponent of making environmental changes where the default option is the healthier option. The trans fat ban initially was only in New York and California and some small localities across the country, but the major chains saw the writing on the wall and made the shift. In New York City, if you really want to get fries made with partially hydrogenated fat, there are mom-and-pop places that aren’t covered under the legislation that serve them. But if you go into your general, random place, you’ll wind up with the healthier option—fries made without hydrogenated fat.

It’s the same thing with salt. If the default option were lower salt, it wouldn't mean you couldn't add salt. We wouldn't be taking anyone’s freedom away, but you can’t take salt out once it’s added, so that would be the healthier default option.

Do you plan to follow up on this work?

I would love to expand the scope of the foods that we look at as well as examine other trends. I think it’s important to note that some venues are introducing healthier options. I believe that most venues for prepared food want to sell more food, and so they will respond to consumer demand. If we had a higher proportion of the population purchasing healthier options, we would see a greater number of healthier options. That comes from educating children when they’re young, and having a campaign to educate those adults who would be receptive now.

We also have to take a slightly different approach to counseling people who need to reduce their caloric intake to lose weight and perhaps cut sodium and saturated fat intake. The simple message to order smaller portions is certainly good if the choice is only small, medium or large.

But I think we also need to give them additional guidance to think about how frequently they are ordering these items. And how many items are they actually ordering? Maybe you shouldn’t automatically order fries with your burger—the same way some places will automatically give you a bag of chips with a sandwich. Even if they’re baked chips or pretzels, they are still extra calories and usually contain refined carbs and extra sodium.

Then there’s using the nutritional information that’s available. There may be three fast-food places that are relatively close. Do a one-time comparison for that item that you normally order. See how much sodium or how many calories are in that item at each restaurant. What we found is that there is a wide range, so settle on the venue that provides fewer calories or lower sodium.

Jacqueline Mitchell can be reached at jacqueline.mitchell@tufts.edu.