On any given day, about one in three adult Americans eats fast food. There are some problems associated with this.

Lots of research suggests fast food isn't good for you, and it's been linked to the obesity epidemic affecting millions in the US, among a host of other issues related to health.

But according to new research, the main reason people avoid fast food isn't simply because it's unhealthy. Rather, they're motivated by feelings of guilt.

In a new study that surveyed over 300 respondents via an online questionnaire, researchers sought to identify the key factors differentiating people who identified themselves as regular fast food consumers or non-regular consumers.

"A gap in research is that reasons for not consuming fast food [are] relatively unknown, other than anecdotal assumptions that low nutritional quality of fast food may discourage fast food consumption," a team led by first author and hospitality management researcher Kiwon Lee from Kent State University in Ohio explains in the paper.

While nutritional quality or lack thereof is certainly a factor in people's minds when they're thinking about fast food, it's just one of many potential things we weigh up when seeking out our next meal.

In the survey, respondents were asked to indicate how much importance they placed on a range of items relating to fast food, including functional values (eg. convenience, taste, familiarity) and emotional values (eg. pleasure) among several other questions – probing participants on everything from food poisoning risks to animal welfare concerns and the environmental impacts of fast food production.

Using a range of statistical techniques to balance and interpret the raw data, the researchers found two key discriminating factors in particular that identified non-regular fast food consumers.

The first factor was their reported tendency to consume fast food in 'accidental situations' somewhat beyond their control – such as in moments of time pressure, when traveling, running out of food at home, or in times of stress. (By contrast, people who voluntarily opt to eat fast food regularly probably don't do so 'accidentally' as much.)

But it's the second discriminating factor for non-regular fast food consumers that more plainly explains why they don't eat fast food the rest of the time. According to the analysis, what makes them abstain the most is… guilt.

"Non-regular consumers can be characterized by the tendency to feel guilty about fast food consumption and feel accomplished when not consuming fast food," the researchers explain.

"Interestingly, unhealthiness, which is frequently addressed as a major problem of fast food and anecdotally assumed as a major reason for avoiding fast food, was not influential in discriminating regular consumers and non-regular consumers."

This result suggests that knowledge of poor nutritional quality is not enough to sway someone's habits on fast food consumption, something that has been found in previous research as well.

"It can be assumed that perceived unhealthiness of fast food leads to the avoidance of consumption only when the perception is accompanied by other reasons to stop eating fast food – such as the feeling of guilt as suggested by our results," the team writes.

The researchers acknowledge that the sample size of their study was relatively small, and therefore suggest caution is needed when generalizing their results. Additionally, to keep their initial survey manageable, they only quizzed people on burgers and fries, although the research design can now be expanded to larger data sets and more fast food groups.

Importantly, the team says obesity prevention programs could stand to gain ground by focusing their messaging around 'guilt appeal' – seeking to shift consumers away from fast food with persuasive techniques designed to emphasize the guilt they'll feel if they eat it.

This could be useful, but the findings go both ways.

In addition to identifying discriminating factors that typify non-regular consumers, the researchers also extracted some of the key factors that differentiate regular fast food eaters: notably convenience and taste, but also concerns over the potential unsafeness of fast food (which probably weighs more on your mind if you're the kind of person who eats a lot of it).

Those insights, the team says, could soon be directed at all of us in the form of newly optimized advertising campaigns – whether we're just accidental customers, or eager regulars.

The findings are reported in Food Quality and Preference.