The gap is mostly in how the food is made, not the food itself
The strongest explanation in this evidence is about preparation. When researchers asked people to picture healthy and unhealthy foods, healthy items came to mind in their purest, least-prepared state, while unhealthy items came to mind fully prepared and ready to eat, like a beef burger in a bun with melted cheese [1]. Cooking, adding toppings, and assembling a dish are exactly the steps that make food taste good, so the foods we think of as unhealthy get credited with all that flavor while the healthy versions get pictured plain [1].
This is a mental habit rather than a fact about nutrients. The effect appears both when people sort images and when they sort words, and in explicit tasks as well as implicit association tasks, which measure automatic associations rather than deliberate answers [1]. The researchers tie it to a perceived conflict between health and taste: because preparation makes food more delicious, a food that is heavily prepared becomes harder to categorize as healthy, so healthy food ends up represented as unprepared [1]. People who feel that health and taste pull against each other most strongly show the effect most strongly [1].
Taste is a top reason people pick the junk
In studies of South African adolescents and their school food environments, taste preference was a major driver of food choices, alongside satiety, value for money, affordability, convenience, and visual appeal [2][4]. The unhealthy ultra-processed foods, such as packaged foods and fast foods, were described as tasty but unhealthy, and they were still preferred [2][4]. Notably, the students had some general nutrition knowledge, but that knowledge did not turn into healthy choices [2][4]. Knowing a food is better for you does not make it win on taste.
The setting matters for how far this goes. These findings come from two public high schools and 42 adolescents aged 14 to 18 in South Africa, and the researchers describe unhealthy foods as widespread in that environment while healthy foods were scarce, which limited what students could choose [2][4]. So taste was a major driver in a place where the tasty option was also the easy one to find.
Describing how a healthy dish was made makes it more appealing
If the problem is that healthy food is imagined as unprepared, then emphasizing preparation should help, and it does. In an experiment that changed the descriptive language on a restaurant menu, highlighting how healthy foods were prepared increased participants' preference for those healthy foods, with no improvement for the unhealthy ones [1]. That is a useful, concrete result: the same dish can sound more delicious when its cooking is made visible.
This fits with the adolescent findings, where visual appeal and satiety were among the drivers of choice [2][4]. A healthy option that is described as cooked, seasoned, and filling is competing on the same terms as the junk food, rather than being pictured as a plain ingredient.
The preference is not fixed, and it can shift
There is a hint that the pull toward junk food is not permanent. Among people using GLP-1 medications, one study found stronger implicit preferences for healthy foods when evaluations were based on enjoyment and taste, compared with non-users [3]. The difference appeared for semaglutide users but not tirzepatide users, and explicit ratings of healthiness, tastiness, and irresistibility did not differ by medication status, suggesting semaglutide users may not be aware of this implicit preference [3]. This is an association, not proof that the medication causes the shift, and it does not explain why junk food tastes good in the first place.
Taken together, the evidence points to a practical answer: junk food wins much of its advantage from being prepared, described, and made easy to find, while healthy food is mentally filed away as something plain and raw [1][2][4]. Changing how healthy food is prepared and presented, and making it affordable and filling, is the lever these studies suggest [1][2][4].
Sources used in this answer
Thinking of food: The mental representation of healthy foods as unprepared
People mentally represent healthy foods in their least-prepared forms and unhealthy foods in their most-prepared forms, and emphasizing preparation on a menu increased preference for healthy foods.
South African Adolescents’ Perspectives on Healthy and Unhealthy Foods and the Drivers of Their Food Choices in Their School Food Environment
South African adolescents named taste preference as a major driver of food choices, describing ultra-processed foods as tasty but unhealthy yet still preferred, and their nutrition knowledge did not translate into healthy choices.
GLP-1 medication use is associated with stronger implicit preferences for healthy foods based on enjoyment and taste
GLP-1 medication users, particularly semaglutide users, showed stronger implicit preferences for healthy foods based on enjoyment and taste than non-users, while explicit ratings did not differ.
Urban South African Adolescents’ Perspectives on Healthy and Unhealthy Foods and the Drivers of Their Food Choices in Their School Food Environment: A Pilot Study
In urban South African schools, unhealthy ultra-processed foods were widespread and healthy foods scarce, with taste preference a major driver of adolescents' food choices.
Perceptual salience influences food choices independently of health and taste preferences
Perceptual salience influenced food choices independently of health and taste preferences.