Little change seen in fast food portion size, product formulation between 1996 and 2013

"There is a perception that restaurants have significantly expanded their portion sizes over the years, but the fast food we assessed does not appear to be part of that trend," said Lichtenstein, who is also the Stanley N. Gershoff Professor at the Friedman School of Nutrition Science and Policy at Tufts University. "Our analysis indicates relative consistency in the quantities of calories, saturated fat, and sodium. However, the variability among chains is considerable and the levels are high for most of the individual menu items assessed, particularly for items frequently sold together as a meal, pushing the limits of what we should be eating to maintain a healthy weight and sodium intake."

"For example, among the three chains, calories in a large cheeseburger meal, with fries and a regular cola beverage, ranged from 1144 to 1757 over the years and among restaurants, representing 57% to 88% out of the approximately 2000 calories most people should eat per day," Lichtenstein continued. "That does not leave much wiggle room for the rest of the day."

According to the authors' 2013 data, calorie content of the cheeseburger meal among the three chains represented 65% to 80% of a 2,000 calorie per day diet and sodium content represented 63% to 91% of the recommendation. The U.S. Dietary Guidelines for Americans recommend adults limit their salt intake to a maximum of 2,300 milligrams per day. Depending on the chain, between 1996 and 2013, eating a single 4 oz. cheeseburger could have accounted for 1100 to 1450 mg of daily sodium representing 48% to 63% of target limits.

Lichtenstein and colleagues focused on the four most popular menu items: fries, cheeseburgers, grilled chicken sandwiches, and regular cola, looking for trends in portion size and nutrient content over an 18 year period. They examined 27 items including small, medium and large fries and cola beverages, a grilled chicken sandwich, and 2 oz. and 4 oz. cheeseburgers. The authors used a public database and the internet to access the archived nutrition data.

They found only small fluctuations in calorie content and the amount of saturated fat and sodium. The notable exception was fries, which decreased first in saturated fat in 2001 and then trans fat, likely due to changes to the frying fat. "The decline in trans fat we saw between 2005 and 2009 appears to be related to legislative efforts," Lichtenstein said. "The success of New York City's trans fat ban and others like it, suggest it is worth pursuing these types of approaches because they make the default option the healthier option. Of course, it is important to note that the healthier option in terms of fat does not translate into lower calories or less salt."

Despite public health campaigns, fast food sales remain strong, contributing to our epidemic of obesity and hypertension. "Restaurants can help consumers by downsizing portion sizes and reformulating their food to contain less of these over-consumed nutrients. This can be done, gradually, by cutting the amount of sodium, and using leaner cuts of meat and reduced-fat cheese," Lichtenstein said. "From what we hear some fast-food chains are heading in that direction and also introducing new healthier options. If taken advantage of, these changes should help consumers adhere to the current dietary recommendations."

The authors also note nutrient content varied among similar items from different chains. For example, an order of small fries could differ by as much as 110 calories and 320 mg of sodium from chain to chain. "For this reason our findings strongly suggest that public health efforts promoting reduction of calories and over-consumed nutrients need to shift from emphasizing small, medium and large portion sizes, to additional factors such as actual number of calories and the nutrient content of the items, as is increasingly becoming available at point of purchase," Lichtenstein said. "A 100 calorie difference per day can mean about a 10 pound weight change per year."