There is such a thing as eating too much healthy food, and a study from the McCombs School of Business has found that people tend to overeat when they believe the food they are eating is healthy. 

The team of researchers concluded that this is because consumers assume that healthy foods are less filling and will therefore overeat in an attempt to feel full. They published their findings in the Journal of Association of Consumer Research in 2016. 

In one of the three experiments outlined in the paper, participants were split into two groups and given cookies to eat. One group was told that their cookies were unhealthy and high in sugar, fats and carbohydrates, while the other group was told that their cookies were healthier and high in fiber, protein and vitamins. Afterwards, when participants were asked whether or not they felt full, those in the healthy cookie group reported that they were still hungry, while those who thought they had eaten unhealthy cookies said they were full. 

“But it was exactly the same cookie,” said Rajagopal Raghunathan, UT marketing professor and a member of the research team. “Even before they consume it, people already have this belief that (the healthy cookie) is not going to be as filling.”

Expecting many people would assume the high-fat, high-carbohydrate cookies had more calories than the “healthy” option, the team then wanted to determine whether the participants were simply equating consuming more calories with an expectation of fullness, Raghunathan said.

“With the unhealthy stuff, because (the participants) think it’s high in calories, they don’t eat as much of that because they know they don’t need to eat as much to get their energy,” Raghunathan said. “We wanted to make sure that it wasn’t just that (perception of higher calories) driving the effect.”

To see if participants were simply counting calories, the team conducted a third experiment where participants were given as much popcorn as they wanted while watching a video. Participants in three different groups were told that the popcorn was “healthy,” “nourishing,” or “unhealthy,” but each group was told that the popcorn held the same number of calories. The participants with “healthy” popcorn ate the most, and participants with “unhealthy” popcorn ate the least. The participants with the “nourishing” popcorn ate an intermediate amount.

“We brought their attention to the fact that healthy also means nourishing … which means that they don’t need to eat as much of it in order to function well,” Raghunathan said. “If we move their (attention) to (the fact that) it’s more nourishing … then we should be able to kind of switch off the effect so that people won’t be eating as much of the stuff that’s portrayed as healthy.” 

The team concluded that consumers tend to equate healthiness with a need to eat more in order to feel energetic and full, Raghunathan said. Regardless of nutrition facts or number of calories, participants ate more of options portrayed as “healthy.” 

“There are many factors that could lead to (feeling full), including … the presence of specific macronutrients such as fat or protein (or) fiber,” UT nutritional sciences lecturer Drew Hays said. “I certainly wouldn’t say that higher calorie foods would make you feel fuller all the time. ”

In advertising, food producers often exploit this tendency to overeat healthy foods, Raghunathan said. Producers may try to trick customers into thinking their product is healthy so that they will consume more of it.

“On the one hand, the consumer, the (Food and Drug Administration) and the American community would want people to not rely on the healthy-equals-less-filling belief,” Raghunathan said. “But on the other hand, there’s no incentive for the producers … to not want their consumers to consume more and more of it.” 

While some claims suggesting the health value of a food are regulated by the U.S. Department of Agriculture, such as “low-sodium” or “organic” labels, more vague terms that imply healthiness are not monitored, Hays said. 

“Something like ‘promotes digestive health’ is just some made up claim and is not regulated,” Hays said. “Things like ‘superfoods’ are marketing terms … those are just to get people to buy the products.”