An ancient survival instinct may explain why we crave junk food during uncertain times

New research published in Food Quality and Preference provides evidence that people are more visually drawn to high-calorie foods when they anticipate future scarcity, especially in contexts that feel unstable or resource-poor. Using eye-tracking technology, the study showed that participants were quicker to fixate on, looked longer at, and rated high-calorie foods as more desirable—particularly if they imagined living in a world marked by economic uncertainty.

Across evolutionary history, the threat of food shortages has shaped human behavior in powerful ways. When resources are uncertain, people tend to seek out energy-dense foods that offer more calories per bite. This tendency may have been adaptive in ancestral environments, where finding enough food was often a matter of survival.

Today, this ancient preference may still influence eating behavior—especially in environments that signal danger, poverty, or instability. Researchers led by Ray Garza wanted to explore how cues from the environment interact with individual concerns about future food access.

“Evolutionary perspectives on eating behavior suggest that humans have always faced harsh environments, and prioritizing energy dense foods is a solution to a recurring adaptive problem of food insecurity,” said study author Ray Garza, an assistant professor of psychology and head of the Evolutionary Visual Lab at Texas A&M International University.

“Previous research shows that ecological cues of harshness (i.e., resources scarcity/violence) and anticipated food scarcity prompt individuals to select high-caloric foods. We wanted to explore the underlying mechanisms involved, such as visual attention indexed by tracking eye-movements. Most studies have relied upon survey data, and we wanted to utilize an experimental approach using eye-tracking.”

To investigate this, the researchers designed an experiment that exposed people to imagined ecological conditions before measuring their attention to different foods. A total of 142 participants, primarily women attending a predominantly Hispanic-serving university in Texas, were randomly assigned to one of three priming scenarios. One scenario portrayed a stable, resource-rich environment (safe condition). Another highlighted economic instability through scenes of job loss and foreclosures (resource scarce condition). The third emphasized violent, dangerous environments using imagery related to crime (violent condition).

After reading or viewing their assigned scenario, participants were calibrated to an eye-tracking device and shown 80 paired images of food items—each pair featuring one high-calorie and one low-calorie option. The eye-tracking software measured how quickly participants looked at the foods, how long they looked at them, and how often they returned their gaze. Participants also completed a food desirability task where they rated the appeal of 30 food images and estimated the number of calories in each item.

The researchers also assessed a range of individual differences. Participants filled out questionnaires measuring their hunger level, socioeconomic background, and a specific scale designed to assess anticipated food scarcity—a person’s belief that food shortages will likely occur in the future. This allowed the team to examine how personal expectations about scarcity interacted with the priming scenarios to influence food attention and preferences.

Across all conditions, participants were faster to look at high-calorie foods and spent more time visually attending to them compared to low-calorie foods. They also rated high-calorie foods as more desirable overall. These effects were seen even when controlling for hunger and socioeconomic status, suggesting a generalized preference for energy-dense foods.

But the most important findings emerged when individual beliefs about food scarcity were taken into account. Among people who anticipated more food scarcity, the priming condition made a difference. In the resource scarce scenario, those with higher food scarcity beliefs were more likely to look at high-calorie foods for longer and fixate on them more frequently. They also rated those foods as more desirable. In contrast, those same individuals did not show a similar preference shift in the violent condition, and in the safe condition, they actually showed slightly more interest in low-calorie foods.

“We did find that when primed with cues of safety, anticipated food scarcity was associated with higher desirability ratings for low-caloric compared to high-caloric foods,” Garza told PsyPost. “Safety cues may prime individuals with availability of resources, which in turn, limits the need for energy-dense food.”

This pattern suggests that not all environmental threats affect eating behavior in the same way. Situations that signal economic deprivation or limited access to food may activate evolved psychological mechanisms that prioritize immediate caloric gains. Violent environments, on the other hand, may generate stress or fear, which can disrupt normal appetite patterns or result in more generalized responses.

The eye-tracking results offered a unique window into the underlying cognitive processes. High-calorie foods were not only more desirable—they were visually prioritized. People with high anticipated food scarcity scores who were primed with resource scarcity directed more visual attention to high-calorie foods, suggesting that these foods are automatically flagged as more important under threat. The findings align with the insurance hypothesis, which proposes that people gravitate toward calorie-dense options as a buffer against future uncertainty.

The researchers interpret these results through the lens of life history theory, an evolutionary framework that explains how organisms adjust their behaviors based on environmental conditions. In unpredictable or harsh environments, a “faster” strategy—focused on immediate rewards rather than long-term planning—may be more adaptive. In this case, a faster strategy may manifest as heightened interest in high-calorie foods, which could provide immediate energy to help survive uncertain times.

“Anticipated food scarcity and cues of resource scarcity affect the way individuals attend to food by viewing high-caloric foods longer,” Garza explained. “This may be to potentially buffer against times of uncertainty, as visual information may influence decision making in eating behaviors.”

There are some limitations to consider. The experiment was conducted in a lab using still images, which may not reflect how people engage with real food in natural settings. Future studies could use wearable eye-tracking glasses in grocery stores or restaurants to examine attention in everyday environments. The sample, drawn largely from female college students, also limits generalizability. It’s unclear whether the same effects would be observed in men or older adults.

“We are looking at investigating other cues of harshness, such as intrasexual competition (i.e., same-sex competition) cues and its role in eating behavior using an eye-tracking paradigm,” Garza said.

The study, “Ecological harshness cues modulate food preferences and visual attention: An eye-tracking study,” was authored by Ray Garza, Dariela Galindo, Karla P. Garcia, and Tiffany Gutierrez.