Gen Z overeating junk food even when full: who’s most likely to keep snacking

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• How the experiment was run: a close look at the design
  • Exactly what the teams matched
• What the buffet test revealed about Gen Z eating habits
• Why the youngest adults may be more vulnerable
  • Potential drivers under investigation
• What counts as an ultra-processed food—and how pervasive they are
• Health stakes: why this matters beyond the buffet
• Limitations, context and next steps planned by the team

The latest research from Virginia Tech raises new alarms about the foods filling Gen Z plates. In a tightly controlled trial, young adults who ate diets high in ultra-processed foods showed a clear tendency to eat more when presented with a buffet, and that effect was strongest in the youngest participants. The findings deepen concerns about how modern food environments may nudge younger people toward excess calories and long-term health risks.

How the experiment was run: a close look at the design

Researchers recruited men and women aged 18 to 25 and put them on two different diets, one dominated by ultra-processed foods and the other free of them. Each diet phase lasted two weeks, separated by a four-week break. Participants returned to their normal routines between study phases.

Key features of the trial:

• Participants were fed enough food to maintain body weight during each phase.
• The two menus were deliberately matched on many nutritional measures.
• After each diet period, volunteers had an unsupervised buffet breakfast and could eat as much as they wished.

Exactly what the teams matched

The investigators worked to control multiple dietary variables so differences could be attributed to processing, not nutrients. Diets were aligned on:

• Macronutrient breakdown (carbs, fat, protein)
• Fiber and added sugar levels
• Energy density
• Many vitamins and minerals

This rigorous matching lets researchers isolate the effect of food processing itself.

What the buffet test revealed about Gen Z eating habits

After each two-week diet, participants fasted and then faced a buffet with both wholesome options and highly processed selections. The tray available contained about 1,800 calories, and individuals could take as much or as little as they wanted.

Results were striking when analyzed by age:

• Those aged 18 to 21 ate more calories following the ultra-processed diet phase.
• They were also more likely to continue eating when not hungry.
• Participants aged 22 to 25 showed less of this overeating pattern.

In short, the younger group responded to prior exposure to processed foods by consuming more at the buffet. Age within this young-adult window mattered.

Why the youngest adults may be more vulnerable

Scientists propose behavioral and biological explanations for the age pattern. Late adolescence and early adulthood are times when motivation and reward systems are still developing. That could make younger people more susceptible to cues that promote overeating.

One of the lead researchers noted the study suggests “younger age as a possible risk factor” for increased calorie intake after consuming ultra-processed foods. But the team also emphasized more work is needed to identify the precise mechanisms.

Potential drivers under investigation

• Heightened reward sensitivity to palatable food cues
• Habituation to strong flavors and textures common in processed products
• Social and environmental factors that encourage snacking and fast consumption

What counts as an ultra-processed food—and how pervasive they are

Ultra-processed foods, often high in additives, flavor enhancers and engineered textures, dominate many young people’s diets. One background statistic highlighted by the researchers is that young adults get roughly 62% of their daily calories from UPFs.

Examples of common UPFs include packaged snacks, many fast-food items, sweetened beverages and some ready-to-eat frozen meals. These products are formulated for convenience and strong sensory appeal.

Health stakes: why this matters beyond the buffet

Evidence links diets heavy in ultra-processed foods to worse health across many domains. Studies associate UPF consumption with elevated risks for cardiovascular disease, certain cancers, Type 2 diabetes, mental health problems and shortened lifespan.

• UPF exposure has been associated with more than 30 negative health outcomes in prior research.
• Public health projections warn that, without changes, obesity rates in teens and young adults could rise dramatically.
• One projection suggests nearly 1 in 3 Americans aged 15 to 24 may meet obesity criteria by 2050.

Limitations, context and next steps planned by the team

The Virginia Tech team stresses this was a short-term, tightly controlled study with a modest number of participants. Still, the design allowed them to hold many nutritional factors steady and focus on how processing alone affected intake.

Researchers plan to expand the work with:

• More participants to boost statistical power
• Younger age groups to see if effects begin earlier
• Longer diet periods to test whether increased intake persists
• Settings that better reflect real-world access to ultra-processed foods

The full report appears in the journal Obesity and adds to growing evidence that the type of food processing matters for appetite and health.